Ignore qualifiers when hashing aro.QualType

[steeve]

Closes #228

[Vexu]

That diff was not intended as a complete fix as it does not address all the sites where anonymous_record_field_names is used. A good fix would be to make the hash map use a custom context which ignores the qualifiers when hashing. This same issue also applies to all other hashmaps keyed on QualTypes which is why foo is not detected as a member function but bar is:

struct Foo {
    int a;
};
extern int foo(const struct Foo *);
extern int bar(struct Foo *);

[steeve]

Updated. Not sure about if this is how you'd like it shape for the code, but it works.