Clang: Enable exceptions explicitly

For some reason, clang 3.8.0 on Windows does not enable exceptions anymore,
which leads to parse errors in MSVC headers (reported upstream [1]).

With this change, we can finally parse main/mainwindow.cpp of a Qt Widgets
Application for a MSVC2015 Kit and libclang 3.8.0 without any error.

[1] https://llvm.org/bugs/show_bug.cgi?id=27324

Change-Id: I532ad4852a06318baf083d363378bc577b3c4309
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>

src/plugins/clangcodemodel/clangutils.cpp

@@ -91,6 +91,7 @@ public:
         optionsBuilder.addTargetTriple();
         optionsBuilder.addLanguageOption(fileKind);
         optionsBuilder.addOptionsForLanguage(/*checkForBorlandExtensions*/ true);
+        optionsBuilder.enableExceptions();
 
         optionsBuilder.addToolchainAndProjectDefines();
         optionsBuilder.undefineCppLanguageFeatureMacrosForMsvc2015();