Implementations of the issue and wait version of __tgt_target_data_begin_mapper.
Passing handle as input/output argument to __tgt_target_data_begin_mapper_<issue|wait>.
- The diff ended up weird, I just added the declarations and definitions for __tgt_target_data_begin_mapper_issue and __tgt_target_data_begin_mapper_wait. I didn't deleted any code.
I think these API functions should also include the source location pointer from https://reviews.llvm.org/D87946. We need to consider renaming the *_issue and *_wait functions to extend the *_loc API the aforementioned patch is introducing. E.g. after D87946 the "current" data begin API function will be __tgt_target_data_begin_mapper_loc, so this patch should extend that name as __tgt_target_data_begin_mapper_loc_issue and __tgt_target_data_begin_mapper_loc_wait. Because both patches make changes to the API, I think it's better to wait until the former patch has been committed.
We've also been talking about extending the API to optionally include declaration names in the mappers so we can refer to mapped variables by name in error and information messages. If we're breaking the API it's probably best to do it all at once so I'm not sure how soon we'll be able to push D87946.