Port build to gcc -fcheck-pointer-bounds

Port build to gcc -fcheck-pointer-bounds

This does not let Emacs run, just build.
* lib-src/etags.c (main):
* lib-src/profile.c (main):
Use return, not exit.
* src/bytecode.c (BYTE_CODE_THREADED) [__CHKP__]:
Do not define, as -fcheck-pointer-bounds is incompatible with taking
addresses of labels.
* src/menu.c (Fx_popup_dialog): Use eassume, not eassert,
to pacify gcc -fcheck-pointer-bounds -Wnull-dereference.