Created by: egrimley
When mangling an ISB instruction we need the PC of the following instruction, which will be the target after flushing fragments. Previously we used get_app_instr_xl8(next_instr), but the next instruction might be instrumentation, in which case the translation fails. So use get_app_instr_xl8(instr) + AARCH64_INSTR_SIZE, instead.
Also, because of the potential side exit, terminate a basic block on OP_isb, enforce this rule in client_process_bb(), and document this restriction.
Fixes #2509 (closed)
Change-Id: Ifcedb70fae7360c791e5857813b4d8d55fdc7471