C++: fix follow symbol for const arguments

Fixed case:

class Foo {};
void foo(int v) {}
void foo(const char *v) {}
void foo(const Foo &v) {}
void foo(char v) {}

void test()
{
    foo(5);
    foo("hoo");
    foo('a');
    char *var = "var";
    foo(var); // Jumps to last override, regardless of its type
    Foo f;
    foo(f); // Jumps to last override
}

Task-number: QTCREATORBUG-13128
Change-Id: I038553bb3bdbe1c300fc01573c14b6fedf0320cd
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/cplusplus/ResolveExpression.h

@@ -77,7 +77,6 @@ protected:
     void addResults(const QList<LookupItem> &items);
 
     static bool maybeValidPrototype(Function *funTy, unsigned actualArgumentCount);
-    bool implicitConversion(const FullySpecifiedType &sourceTy, const FullySpecifiedType &targetTy) const;
 
     using ASTVisitor::visit;