Like for functions we can call attemptFuncDeclDef for operators. The
check for function names has been enhanced to take operators into
account.
For the switch from definition to declaration
SymbolFinder::findMatchingDeclaration has been enriched with operator
knowledge.

Task-number: QTCREATORBUG-7485

Change-Id: I29eebee337e26c8bf67dc8b4a15c43883045589d
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>