final patch for very long conditional branches for mips16 constant islands.
this completes the basic port of ARM constant islands to Mips16.
More testing, code review, cleanup is in order but basically everything
seems to be working. A bug in gas is preventing some of the runtime
testing but I hope to resolve this soon.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196331 91177308-0d34-0410-b5e6-96231b3b80d8