[OMPT] Update types according to TR7

Some types and callback signatures have changed from TR6 to TR7.
Major changes (only adding signatures and stubs):
(-remove idle callback) done by D48362
-add reduction and dispatch callback
-add get_task_memory and finalize_tool runtime entry points
-ompt_invoker_t  becomes ompt_parallel_flag_t
-more types of sync_regions

Patch provided by Simon Convent

Reviewers: hbae, protze.joachim

Differential Revision: https://reviews.llvm.org/D50774

llvm-svn: 341834