SymbolDatabase: Variable::isReference() is true for function pointer returning a reference

[autoantwort]

struct S {
    std::string& (*f)(int, int);
    int& (*g[2])();
};
void foo(int& (*fp)(), int&& (*fp2)());

Variable::isReference() (and isRValueReference() for fp2) is true for f, g, fp and fp2, and their
ValueType has reference == Reference::LValue/RValue. The reference belongs to the return type of the function
pointer, the variables themselves are pointers (or an array of pointers). Real references to function pointers like
int (*&f)() are correct.

Variable::evaluate() sets the reference flag for every & between the type start and end token, which includes the
return type of a function pointer before the (. parsedecl() keeps the reference of the return type as well.

Found with PR #8910 (​https://github.com/cppcheck-opensource/cppcheck/pull/8910), where it suppressed
uninitMemberVarNoCtor for a struct with such a member (codelite in the PR test results). #8910 contains a workaround
in CheckClass that can be removed after this is fixed.