Adds a new header export mechanism, DR_export_header(). This is a copy with variable expansion but no other changes. The idea of this refactoring is to have simple copied entire headers without the patchwork export selection from the middle of regular headers that we have today with genapi.pl.
Uses the new mechanism for dr_api.h and dr_app.h, which were already copied.
Cleans up dr_inject.h and dr_config.h and exports them directly.
Refactors core/annotations.h to separate out annotations_api.h, which is directly copied to include/dr_annotation.h and is excluded from passing through genapi.pl. It has the target name in its include guard, and it has DR_API decoration which is defined as a nop in dr_defines.h.
This is an incremental step toward refactoring all our header exports and eliminating genapi.pl.
Issue: #3092 (closed)