Implement code completion for tags, e.g., code completion after "enum"
will provide the names of various enumerations currently
visible. Introduced filtering of code-completion results when we build
the result set, so that we can identify just the kinds of declarations
we want.

This implementation is incomplete for C++, since we don't consider
that the token after the tag keyword could start a
nested-name-specifier. 



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@82222 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed