[C++] Rewrite of the preprocessor.

This rewrite fixes a couple of issues with the pre-processor. It now
supports:
- macros in macro bodies
- stringification of parameters [cpp.stringize]
- the concatenation operator [cpp.concat]
- #include MACRO_HERE
- defined() inside macro bodies used in pp-conditions.

Change-Id: Ifdb78041fb6afadf44f939a4bd66ce2832b8601f
Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>

tests/auto/cplusplus/preprocessor/data/macro-test.cpp

@@ -0,0 +1,36 @@
+#define USE(MY_USE) (defined MY_USE_##MY_USE && MY_USE_##MY_USE)
+
+#define MY_USE_FEATURE1 1
+#define MY_USE_FEATURE2 0
+
+#if USE(FEATURE1)
+void thisFunctionIsEnabled();
+#endif
+
+#if USE(FEATURE2)
+void thisFunctionIsDisabled();
+#endif
+
+#if USE(FEATURE3)
+void thisFunctionIsAlsoDisabled();
+#endif
+
+#define USE2(MY_USE) (defined MY_USE_##MY_USE)
+
+#if USE2(FEATURE1)
+void thisFunctionIsEnabled2();
+#endif
+
+#if USE2(FEATURE3)
+void thisFunctionIsDisabled2();
+#endif
+
+#define USE3(MY_USE) (MY_USE_##MY_USE)
+
+#if USE3(FEATURE1)
+void thisFunctionIsEnabled3();
+#endif
+
+#if USE3(FEATURE2)
+void thisFunctionIsDisabled3();
+#endif