* src/keyboard.c (requeued_events_pending_p): Improve name and fix comment

* src/keyboard.c (requeued_events_pending_p): Improve name and fix comment

* src/keyboard.c, src/keyboard.h (requeued_events_pending_p): Rename to
'requeued_command_events_pending_p' to clarify that the function covers
only command events. Fix wrong comment that claimed that the function
was unused.
* src/process.c (wait_reading_process_output): Update caller to use the
new name.

(cherry picked from commit 385a02cffde6d0fd80ff189704ad70cfebc3e8d4)