(mips_elf_local_got_index): Use the hash table entry to record
the GOT index of forced-local symbols.
(mips_elf_initialize_tls_index): Rearrange code. Store the index
in either the hash table entry or the mips_got_entry, not both.
Add more commentary.
(mips_elf_multi_got): Make sure the g->next is nonnull when calling
mips_elf_initialize_tls_index.
* ld-mips-elf/tls-hidden3a.s, ld-mips-elf/tls-hidden3b.s,
* ld-mips-elf/tls-hidden3.d, ld-mips-elf/tls-hidden3.got,
* ld-mips-elf/tls-hidden3.ld, ld-mips-elf/tls-hidden3.r,
* ld-mips-elf/tls-hidden4a.s, ld-mips-elf/tls-hidden4b.s,
* ld-mips-elf/tls-hidden4.got, ld-mips-elf/tls-hidden4.r: New tests.
* ld-mips-elf/mips-elf.exp: Run them.
