gas/read.c: init more statics

	* read.c (current_name, current_label, dwarf_file, dwarf_line): Move
	to file scope.
	(pobegin): Tidy pop_override_ok.
	(read_a_source_file): Make last_eol an auto var.
	(s_reloc): Constify bfd_relocs.
	(read_begin): Init more variables.