* corefile.h: Rename from core.h.
* Many .c files: Include corefile.h rather than core.h.
* Makefile.am (sources): Change core.c to corefile.c.
(noinst_HEADERS): Change core.h to corefile.h.
($(OBJECTS)): Depend upon corefile.h rather than core.h.
(corefile.o): Rename target from core.o, depend upon corefile.c.
* Makefile.in, po/POTFILES.in: Rebuild.