gas: fix a few omissions in .cfi_label handling

gas: fix a few omissions in .cfi_label handling

While actually starting to use that new directive, I noticed a few
oversights of the original commit.

gas/
2015-02-06  Jan Beulich  <jbeulich@suse.com>

	* dw2gencfi.c (select_cie_for_fde): Also bail on CFI_label.
	(cfi_change_reg_numbers): Also do nothing for CFI_label.
	(cfi_pseudo_table): Also handle .cfi_label when not supporting
	CFI directives.