Add "follow reference" to go to typedef

[Mortal]

Currently, clang_complete does not support following definitions very well in code like this:

template <typename T, typename A>
struct factory {
	A value;
	factory(A value) : value(value) {}
	T construct() { return T(value); }
};

struct Foo {
	Foo(int) {}
};

typedef factory<Foo, int> foo;

struct Bar {
	Bar(float) {}
};

typedef factory<Bar, float> bar;

int main() {
	auto x = foo(42).construct();
	auto y = bar(123.0).construct();
	return 0;
}

I want to go from foo in main() to the typedef factory<Foo, int> foo; line. However, C-] (or g:ClangGotoDeclaration) goes straight through the typedef to the definition of factory::factory, which is useless. After some print-debugging, it seems that in function gotoDeclaration, neither cursor.get_definition() nor cursor.referenced returns a cursor to the typedef; both return cursors to the constructor. From my limited experimentation it seems to only occur when the typedef is for a templated type.

(Of course, this is a trivial example. For a challenge, I dare you to try finding the definition of buffer used in this function. clang_complete currently can only take you to something called pipe_middle which is not what you want. grep is useless since the word buffer is used all over the codebase.)

Fortunately, cursor.type.get_declaration() goes to the typedef. This patch adds support for going to that cursor and thus fixes the problem.

I've added map \g :call g:ClangGotoDeclaration()<CR> to my vimrc (mimicking jedi-vim's function for that binding, and now I can go to the typedef using that binding.

[adam900710]

That's the function I'm always dreaming of.
It's especially important for me to viewing qemu code (tons of typedef in a seperate header)

In fact I has already modified my local libclang.py to do extra type checks and follow canonical type to get its declaration.

Can't wait to see this get merged.