MSVC: vsnprintf in Visual Studio 2015 doesn't need SNPRINTF_SIZE_CORR any more

In MSVC2015 the behavior of vsnprintf was changed.
W/o this fix there is one character missing at the end.

Signed-off-by: Sven Strickroth <sven@cs-ware.de>
Acked-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Acked-by: Sebastian Schuberth <sschuberth@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Sven Strickroth

compat/snprintf.c

@@ -9,7 +9,7 @@
  * always have room for a trailing NUL byte.
  */
 #ifndef SNPRINTF_SIZE_CORR
-#if defined(WIN32) && (!defined(__GNUC__) || __GNUC__ < 4)
+#if defined(WIN32) && (!defined(__GNUC__) || __GNUC__ < 4) && (!defined(_MSC_VER) || _MSC_VER < 1900)
 #define SNPRINTF_SIZE_CORR 1
 #else
 #define SNPRINTF_SIZE_CORR 0