Move declarations from .c files to .h files.

Move declarations from .c files to .h files.

* src/process.c (timers_run):
* src/minibuf.c (quit_char):
* src/lread.c (read_emacs_mule_char):
* src/keyboard.c (minibuf_level, message_enable_multibyte)
(pending_malloc_warning):
* src/insdel.c (Vselect_active_regions, Vsaved_region_selection)
(Qonly): Remove declarations.
* src/lisp.h (pending_malloc_warning, Vsaved_region_selection)
(Vselect_active_regions):
* src/keyboard.h (timers_run):  Add declarations.