Cppcheck: Add ability to manually run cppcheck

Run cppcheck on selected files from current project via "Analyze"->"Cppcheck...."
Show results in a separate view in the same manner as ClangTools plugin.

Fixes: QTCREATORBUG-21673
Change-Id: Ibcaf4057a387a990f1da59025f15ba58f996953f
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cppcheck/cppcheckdiagnostic.h

@@ -39,6 +39,7 @@ public:
     bool isValid() const {
         return !fileName.isEmpty() && lineNumber > 0;
     }
+    bool operator==(const Diagnostic& diagnostic) const;
 
     Severity severity = Severity::Information;
     QString severityText;
@@ -48,5 +49,7 @@ public:
     int lineNumber = 0;
 };
 
+quint32 qHash(const Diagnostic &diagnostic);
+
 } // namespace Internal
 } // namespace Cppcheck