Enable C11/C++11

See arduino/Arduino#2175

Quoting the original commits from Matthijs Kooijman:

    Enable C++11 support

    This uses the gnu++11 standard, which is C++11 with GNU extensions.
    C++11 should be full compatible with the previously used C++98
    standards, so all pre-existing sketches should continue to work.

    Enable C11 support

    This uses the gnu11 standard, which is C11 with GNU extensions.
    Previously, gnu89 was being used, which is pretty ancient by now. C99
    brings some important improvements, some of which were already available
    and used even without this option. C11 is more recent and brings more
    minor improvements. Most notable feature is the static_assert statement,
    allowing checking invariants at compiletime using the full C
    expressions.

Author: cmaglie

cores/arduino/WString.cpp

@@ -45,7 +45,7 @@ String::String(const __FlashStringHelper *pstr)
 	*this = pstr;
 }
 
-#ifdef __GXX_EXPERIMENTAL_CXX0X__
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 String::String(String &&rval)
 {
 	init();
@@ -191,7 +191,7 @@ String & String::copy(const __FlashStringHelper *pstr, unsigned int length)
 	return *this;
 }
 
-#ifdef __GXX_EXPERIMENTAL_CXX0X__
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 void String::move(String &rhs)
 {
 	if (buffer) {
@@ -223,7 +223,7 @@ String & String::operator = (const String &rhs)
 	return *this;
 }
 
-#ifdef __GXX_EXPERIMENTAL_CXX0X__
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 String & String::operator = (String &&rval)
 {
 	if (this != &rval) move(rval);

cores/arduino/WString.h

@@ -1,5 +1,8 @@
 /*
-  Copyright (c) 2014 Arduino.  All right reserved.
+  WString.h - String library for Wiring & Arduino
+  ...mostly rewritten by Paul Stoffregen...
+  Copyright (c) 2009-10 Hernando Barragan.  All right reserved.
+  Copyright 2011, Paul Stoffregen, paul@pjrc.com
 
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
@@ -8,8 +11,8 @@
 
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-  See the GNU Lesser General Public License for more details.
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
 
   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free Software
@@ -56,7 +59,7 @@ class String
 	String(const char *cstr = "");
 	String(const String &str);
 	String(const __FlashStringHelper *str);
-	#ifdef __GXX_EXPERIMENTAL_CXX0X__
+       #if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	String(String &&rval);
 	String(StringSumHelper &&rval);
 	#endif
@@ -78,21 +81,21 @@ class String
 	inline unsigned int length(void) const {return len;}
 
 	// creates a copy of the assigned value.  if the value is null or
-	// invalid, or if the memory allocation fails, the string will be
+	// invalid, or if the memory allocation fails, the string will be 
 	// marked as invalid ("if (s)" will be false).
 	String & operator = (const String &rhs);
 	String & operator = (const char *cstr);
 	String & operator = (const __FlashStringHelper *str);
-	#ifdef __GXX_EXPERIMENTAL_CXX0X__
+       #if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	String & operator = (String &&rval);
 	String & operator = (StringSumHelper &&rval);
 	#endif
 
 	// concatenate (works w/ built-in types)
-
+	
 	// returns true on success, false on failure (in which case, the string
-	// is left unchanged).  if the argument is null or invalid, the
-	// concatenation is considered unsucessful.
+	// is left unchanged).  if the argument is null or invalid, the 
+	// concatenation is considered unsucessful.  
 	unsigned char concat(const String &str);
 	unsigned char concat(const char *cstr);
 	unsigned char concat(char c);
@@ -104,7 +107,7 @@ class String
 	unsigned char concat(float num);
 	unsigned char concat(double num);
 	unsigned char concat(const __FlashStringHelper * str);
-
+	
 	// if there's not enough memory for the concatenated value, the string
 	// will be left unchanged (but this isn't signalled in any way)
 	String & operator += (const String &rhs)	{concat(rhs); return (*this);}
@@ -197,7 +200,7 @@ class String
 	// copy and move
 	String & copy(const char *cstr, unsigned int length);
 	String & copy(const __FlashStringHelper *pstr, unsigned int length);
-	#ifdef __GXX_EXPERIMENTAL_CXX0X__
+       #if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 	void move(String &rhs);
 	#endif
 };

platform.txt

@@ -33,13 +33,13 @@ compiler.warning_flags.all=-Wall -Wextra
 
 compiler.path={runtime.tools.arm-none-eabi-gcc.path}/bin/
 compiler.c.cmd=arm-none-eabi-gcc
-compiler.c.flags=-mcpu={build.mcu} -mthumb -c -g -Os {compiler.warning_flags} -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -MMD
+compiler.c.flags=-mcpu={build.mcu} -mthumb -c -g -Os {compiler.warning_flags} -std=gnu11 -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -MMD
 compiler.c.elf.cmd=arm-none-eabi-gcc
 compiler.c.elf.flags=-Os -Wl,--gc-sections -save-temps
 compiler.S.cmd=arm-none-eabi-gcc
 compiler.S.flags=-c -g -x assembler-with-cpp
 compiler.cpp.cmd=arm-none-eabi-g++
-compiler.cpp.flags=-mcpu={build.mcu} -mthumb -c -g -Os {compiler.warning_flags} -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -MMD
+compiler.cpp.flags=-mcpu={build.mcu} -mthumb -c -g -Os {compiler.warning_flags} -std=gnu++11 -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -MMD
 compiler.ar.cmd=arm-none-eabi-ar
 compiler.ar.flags=rcs
 compiler.objcopy.cmd=arm-none-eabi-objcopy