Remove workarounds for unsupported compilers

Change-Id: Ie28ff761b0bae13c6ebdf7dd649cfbba28e0fc2c
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/libs/cplusplus/LookupItem.h

@@ -73,9 +73,3 @@ private:
 uint qHash(const CPlusPlus::LookupItem &result);
 
 } // namespace CPlusPlus
-
-#if defined(Q_CC_MSVC) && _MSC_VER <= 1300
-//this ensures that code outside QmlJS can use the hash function
-//it also a workaround for some compilers
-inline uint qHash(const CPlusPlus::LookupItem &item) { return CPlusPlus::qHash(item); }
-#endif