This allows clients of libclang to check whether a completion result is a keyword. Previously, keywords had CursorKind == CXCursor_NotImplemented and it wasn't trivial to distinguish a keyword from a pattern.
This change moves CodeCompletionResult::ResultKind to clang-c under a new name CXCompletionResultKind. It also tweaks c-index-test to print the result kind instead of NotImplemented, and adjusts the tests for the new output.
rdar://91852088