Removes the no-longer-supported custom exit stub feature: all of the code under the CUSTOM_EXIT_STUBS define and the INSTR_HAS_CUSTOM_STUB flag. Removing the flag frees it up for use in #4180 (closed).
Issue: #4045, #4180 (closed)
Removes the no-longer-supported custom exit stub feature: all of the code under the CUSTOM_EXIT_STUBS define and the INSTR_HAS_CUSTOM_STUB flag. Removing the flag frees it up for use in #4180 (closed).
Issue: #4045, #4180 (closed)