* config/tc-mips.c (append_insn): Use fix_new rather than fix_new_exp

	* config/tc-mips.c (append_insn): Use fix_new rather than fix_new_exp
	to build the second and third fixups for a composite relocation.
	(macro_read_relocs): New function.
	(macro_build): Use it.
	(s_cpsetup): Pass all three composite relocation codes to macro_build.
	Simplify fragging code accordingly.
	(s_gpdword): Use fix_new rather than fix_new_exp for the second part
	of the composite relocation.  Set fx_tcbit in both fixups.