Ignore pending_signals when checking for quits.
pending_signals is often set if no quit is pending. This results in bugs in module code if the module returns but no quit is actually pending. As a better alternative, add a new process_input environment function for Emacs 27. That function processes signals (like maybe_quit). * configure.ac: Add module snippet for Emacs 27. * src/module-env-27.h: New file. * src/emacs-module.h.in: Add process_input function to environment interface. * src/emacs-module.c (module_should_quit): Use QUITP macro to check whether the caller should quit. (module_process_input): New function. (initialize_environment): Use it. * src/eval.c: Remove obsolete comment. * test/data/emacs-module/mod-test.c (signal_wrong_type_argument) (signal_errno): New helper functions. (Fmod_test_sleep_until): New test module function. * test/src/emacs-module-tests.el (mod-test-sleep-until): New unit test. * doc/lispref/internals.texi (Module Misc): Document process_input.