Share cached ParseSessionData with all files in the translation unit.
Review Request #122111 - Created Jan. 17, 2015 and submitted
This still only applies to files open in the editor but already helps there to share the data between header and implementation e.g.
the problem I have with this, is that often no file is open at all. or system headers are pinned to some completely other TU that is currently not being worked on. still, better than nothing. We should now also be able to remove some code duplication in e.g. the signature assistant, which should now assume that both, header and source are part of the same TU. furthermore, the code completion should also be looking for the parsesession data in the context of the TU url for the current document, which is relevant when we open a .h for a .cpp after that was parsed.