Add name for anonymous Enum

[xVanTuring]

ccls/src/indexer.cc

Lines 963 to 965 in bd609e8

	case TTK_Enum:
	tag = "enum";
	break;

Here, case Decl::Record is trying to match enum. However, EnumDecl and RecordDecl are both inherited from TagDecl directly, is, so the matching here will never get executed, which causes the anonymous Enum having no name. So I add a case:: Enum matching above case Decl::Record, and it will add a simple name for anonymous Enum.

Of course, removing the matching code is an alternative solution.
Any edits are welcome.

[MaskRay]

Thanks. This will assign anon enum to an anonymous Enum.

struct A {
  enum {B,C} xx;
};

textDocument/hover on enum will say "anon enum".

[MaskRay]

I deleted this unrelated change when merging.