In Thumb2, direct branches can be encoded as either a "short" conditional branch with a null predicate, or
as a "long" direct branch.  While the mnemonics are the same, they encode the branch offset differently, and
the Darwin assembler appears to prefer the "long" form for direct branches.  Thus, in the name of bitwise
equivalence, provide encoding and fixup support for it.

llvm-svn: 121710