C++: clean up numeric literal parsing and add support for n3472.

Separate the messy pp-number parsing from the numeric literal parsing.
The C/C++ preprocessor makes a grown man cry, but at least we have
"proper" literal parsing when we want it, including C++1y binary
literals.

Next step is digit separators (n3781).

Change-Id: Ia069eef454ed5c056f77694a5b8a595d0b76adc4
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

src/libs/cplusplus/SimpleLexer.h

@@ -51,6 +51,9 @@ public:
     bool skipComments() const;
     void setSkipComments(bool skipComments);
 
+    void setPreprocessorMode(bool ppMode)
+    { _ppMode = ppMode; }
+
     LanguageFeatures languageFeatures() const { return _languageFeatures; }
     void setLanguageFeatures(LanguageFeatures features) { _languageFeatures = features; }
 
@@ -74,6 +77,7 @@ private:
     LanguageFeatures _languageFeatures;
     bool _skipComments: 1;
     bool _endedJoined: 1;
+    bool _ppMode: 1;
 };
 
 } // namespace CPlusPlus