This patch causes local GOT entries addressed via a 16-bit index to

This patch causes local GOT entries addressed via a 16-bit index to
be placed towards the front of local GOT space, while entries addressed
via a 32-bit index are placed towards the rear.

Provided that there are fewer than ~16K local GOT entries addressed via
a 16-bit index in total, this should eliminate any relocation overflows
caused by such GOT entries being allocated beyond the addressable range.

bfd/
	* elfxx-mips.c (struct mips_got_info): Delete assigned_gotno
	field.  Add assigned_low_gotno and assigned_high_gotno fields.
	(mips_elf_create_local_got_entry): Update out-of-space condition.
	Set index of new GOT entry to assigned_low_gotno if required by
	the current relocation, else set it to assigned_high_gotno.
	(mips_elf_set_global_gotidx): Replace uses of assigned_gotno
	with assigned_low_gotno.
	(mips_elf_multi_got): Initialize assigned_low_gotno and
	assigned_high_gotno in secondary GOTs.  Use assigned_low_gotno
	in place of assigned_gotno when handling global GOT entries.
	(mips_elf_lay_out_got): Initialize assigned_low_gotno and
	assigned_high_gotno.
	(_bfd_mips_elf_finish_dynamic_sections): Account for a possible
	gap in the middle of local GOT space.

ld/testsuite/
	* ld-mips-elf/elf-rel-xgot-n32.d: Update for new GOT layout.
	* ld-mips-elf/elf-rel-xgot-n32-embed.d: Likewise.
	* ld-mips-elf/elf-rel-xgot-n64.d: Likewise.
	* ld-mips-elf/elf-rel-xgot-n64-embed.d: Likewise.
	* ld-mips-elf/elf-rel-xgot-n64-linux.d: Likewise.