* Added a mode in swift-ide-test to test code completion. Unlike c-index-test,
the code completion token in tests is a real token -- we don't need to
count lines and columns anymore.
* Added support in lexer to produce a code completion token.
* Added a parser interface to code completion. It is passed down from the
libFrontend to the parser, but its functions are not called yet.
* Added a sketch of the interface of code completion consumer and code
completion results.
Note: all this is not doing anything useful yet.
Swift SVN r6128
