Adds a convenience routine drmgr_in_emulation_region() and flag DR_EMULATE_FIRST_INSTR to make it easier to query emulation markers.
Adds a new flag DR_EMULATE_INSTR_ONLY for expansions where the sequence being executed should be examined for data references and only instruction observation should look at the original instruction. Sets the flag for drutil_expand_rep_string*() and drx_expand_scatter_gather().
Clarifies that the flags field added in PR #4877 is a source compatibility break if source code was not zeroing the full struct.
Ports the emulation_api_simple test to x86_64. Augments the test to perform a partial DR_EMULATE_INSTR_ONLY emulation as well for both platforms. Adds checks for various invariants in the test.
Future work will add emulation awareness to tracing clients.
Issue: #4866 (closed), #4865 (closed) Fixes #4865 (closed)