Follow-ups on #3975 and #4043:
- the PHP language-construct set cited _GO_PREDECLARED_FUNCS, which does
not exist; the real analog is _LANGUAGE_BUILTIN_GLOBALS.
- _EXTERNAL_STUB_RELATIONS said `calls` to an external target is always
suppressed (#3156); after #4043 an imported module does receive a
`calls` edge, so clarify the actual invariant.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>