Introduce common/errors.h

This introduces common/errors.h.  This holds some error- and
warning-related declarations that can be used by the code in common.
Clients of the "common" code must provide definitions for these
functions.

gdb/
2014-07-30  Tom Tromey  <tromey@redhat.com>
	    Gary Benson  <gbenson@redhat.com>

	* common/errors.h: New file.
	* common/errors.c: Likewise.
	* Makefile.in (HFILES_NO_SRCDIR): Add common/errors.h.
	(COMMON_OBS): Add errors.o.
	(errors.o): New rule.
	* common/common-defs.h: Include errors.h.
	* utils.h: (perror_with_name, error, verror, warning, vwarning):
	Don't declare.
	* common/common-utils.h: (malloc_failure, internal_error):
	Likewise.

gdb/gdbserver/
2014-07-30  Tom Tromey  <tromey@redhat.com>
	    Gary Benson  <gbenson@redhat.com>

	* Makefile.in (SFILES): Add common/errors.c.
	(OBS): Add errors.o.
	(IPA_OBS): Add errors-ipa.o.
	(errors.o): New rule.
	(errors-ipa.o): Likewise.
	* utils.h: (perror_with_name, error, warning): Don't declare.
	* utils.c (warning): Renamed and rewritten as...
	(vwarning): New function.
	(error): Renamed and rewritten as...
	(verror): New function.
	(internal_error): Renamed and rewritten as...
	(internal_verror): New function.