Fixes a crash due to jumping in the middle of a routine in the client.signal test, which skips the saving/setting of the frame pointer added in the beginning of routines.
Redirects execution to the beginning of the hook routine, instead of somewhere in the middle which can cause issues if essential code sequences like this are skipped.
Documents a pitfall of using DR_SIGNAL_REDIRECT
or dr_redirect_execution to redirect control to an
arbitrary pc.
Fixes: #5177 (closed)