Add ATTRIBUTE_PRINTF attributes, and fix fallout

Add ATTRIBUTE_PRINTF attributes, and fix fallout

Fixes building gdb on x86_64-apple-darwin14 with clang, which produces
a number of warnings from -Wformat-nonliteral.

Ref: https://sourceware.org/ml/gdb/2015-02/msg00047.html

gdb/ChangeLog:
2015-02-26  Pedro Alves  <palves@redhat.com>

	* auto-load.h (file_is_auto_load_safe): Add ATTRIBUTE_PRINTF.
	* complaints.c (vcomplaint): Pass argument FMT directly to
	printf-like functions instead of complaint->fmt.
	* ctf.c (ctf_save_write_metadata): Add ATTRIBUTE_PRINTF.
	* darwin-nat.c (inferior_debug): Add ATTRIBUTE_PRINTF.
	* compile/compile-loc2c.c (pushf, unary, binary): Add
	ATTRIBUTE_PRINTF.
	(do_compile_dwarf_expr_to_c): Pass string literal as format string
	to pushf.
	(BINARY): Pass string literal as format string to 'binary'.
	* compile/compile-object-load.c (link_callbacks_einfo): Add
	ATTRIBUTE_PRINTF.
	* guile/guile-internal.h (gdbscm_printf): Add ATTRIBUTE_PRINTF.