Clang*: Workaround parsing mingw's <type_traits> with clang 3.9

...for -std=gnu++0x.

Define the unknown identifier/type "__float128" so at least the headers can be
parsed successfully. Of course this does not help for parsing client code
referencing that identifier, but this should be the less common case.

Task-number: QTCREATORBUG-17126
Change-Id: Id321311713029d8aa77e068b02361d86debfada6
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/clangcodemodel/clangutils.cpp

@@ -96,6 +96,7 @@ public:
         optionsBuilder.enableExceptions();
 
         optionsBuilder.addDefineToAvoidIncludingGccOrMinGwIntrinsics();
+        optionsBuilder.addDefineFloat128ForMingw();
         optionsBuilder.addToolchainAndProjectDefines();
         optionsBuilder.undefineCppLanguageFeatureMacrosForMsvc2015();