MIPS/LD: Fix memory fault linking non-PIC object in to shared library

bfd/
	* elfxx-mips.c (_bfd_mips_elf_check_relocs): Add NULL pointer
	checks.  Search the RELA table for n64 relocations.

ld/
	* testsuite/ld-mips-elf/pic-reloc-5.d: New test.
	* testsuite/ld-mips-elf/pic-reloc-6.d: New test.
	* testsuite/ld-mips-elf/pic-reloc-7.d: New test.
	* testsuite/ld-mips-elf/pic-reloc-5.s: New test source.
	* testsuite/ld-mips-elf/pic-reloc-6.s: New test source.
	* testsuite/ld-mips-elf/pic-reloc-7.s: New test source.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.
10 files changed