branch instructions for mips and micromips instruction sets thus avoiding
the situation of generating branches to undesired locations if offsets
cannot be encoded.
This patch also checks if a fixup cannot be applied and returns a fatal error
if that's the case.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197223 91177308-0d34-0410-b5e6-96231b3b80d8
