CPP: Add keyset annotations to the CPP dbscheme.

Author: geoffw0

cpp/ql/src/semmlecode.cpp.dbscheme

@@ -39,6 +39,7 @@ compilations(
  * 5   | f2.c
  * 6   | f3.c
  */
+#keyset[id, num]
 compilation_args(
     int id : @compilation ref,
     int num : int ref,
@@ -62,6 +63,7 @@ compilation_args(
  * Note that even if those files `#include` headers, those headers
  * do not appear as rows.
  */
+#keyset[id, num]
 compilation_compiling_files(
     int id : @compilation ref,
     int num : int ref,
@@ -80,6 +82,7 @@ compilation_compiling_files(
  * 3    | CPU seconds used by the extractor backend
  * 4    | Elapsed seconds during the extractor backend
  */
+#keyset[id, num, kind]
 compilation_time(
     int id : @compilation ref,
     int num : int ref,
@@ -100,8 +103,9 @@ compilation_time(
  * message generated while extracting the `file_number`th file of that
  * invocation.
  */
+#keyset[compilation, file_number, file_number_diagnostic_number]
 diagnostic_for(
-    int diagnostic : @diagnostic ref,
+    unique int diagnostic : @diagnostic ref,
     int compilation : @compilation ref,
     int file_number : int ref,
     int file_number_diagnostic_number : int ref
@@ -124,6 +128,7 @@ compilation_finished(
  * [Tutorial: Incorporating external data](https://help.semmle.com/wiki/display/SD/Tutorial%3A+Incorporating+external+data)
  * for more information.
  */
+#keyset[id, column]
 externalData(
     int id : @externalDataElement,
     string path : string ref,
@@ -167,6 +172,7 @@ similarCode(
 /**
  * Data used by the 'duplicate code' and 'similar code' detection.
  */
+#keyset[id, offset]
 tokens(
     int id : @duplication_or_similarity ref,
     int offset : int ref,