[index] Change SymbolCXXTemplateKind to a 'SymbolSubKinds' bitset.

This provides a more general and flexible way to annotate special symbols.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@267116 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed