Adds rip-relative information tracking at IR levels 1-3 for instruction references on x86, extending the existing tracking for data references.
Adds decode_sizeof_ex() and instr_get_rel_data_or_instr_target() to support rip-relative displacement and target handling.
Changes decode_from_copy() to preserve raw bits for all instructions, eliminating problems where untracked encoding features are lost such as in #4017 (closed).
Documents the changes and describes how to avoid the new behavior. Does just that for intra-sequence cti's in the rseq native code copy.
Adds test cases to api.ir.
Implementing the same thing for AArchXX is left unimplemented, tracked by i#4016.
Issue: #731 (closed), #3271 (closed), #3339, #4016, #4017 (closed) Fixes #731 (closed) Fixes #3271 (closed) Fixes #4017 (closed)