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.cpp

@@ -41,7 +41,8 @@ using namespace CPlusPlus;
 SimpleLexer::SimpleLexer()
     : _lastState(0),
       _skipComments(false),
-      _endedJoined(false)
+      _endedJoined(false),
+      _ppMode(false)
 {}
 
 SimpleLexer::~SimpleLexer()
@@ -73,6 +74,7 @@ Tokens SimpleLexer::operator()(const QString &text, int state)
     Lexer lex(firstChar, lastChar);
     lex.setLanguageFeatures(_languageFeatures);
     lex.setStartWithNewline(true);
+    lex.setPreprocessorMode(_ppMode);
 
     if (! _skipComments)
         lex.setScanCommentTokens(true);