[TCWG-614] Range extension thunks
Started process of upstreaming the conversion of Thunks to SyntheticSections. - Patch 1 of 3 committed, move Thunk Creation later in the link step. - Patch 2 of 3 add support for local symbol creation in upstream review - Patch 3 of 3 waiting for patch 2
Made a patch to output mapping symbols in PLT to test local symbol creation. Not recommending this for inclusion in lld yet, but have included as a way of testing 2.
Responded to comment on implementation and overall Thunks proposal.
Plans for next week: Yet more range extension work, hope to get patches 2 and 3 above committed.