Change indirect-globals to use a dedicated allocIndirectGV. This lets us

Change indirect-globals to use a dedicated allocIndirectGV.  This lets us
remove start/finishGVStub and the BufferState helper class from the
MachineCodeEmitter interface.  It has the side-effect of not setting the
indirect global writable and then executable on ARM, but that shouldn't be
necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91464 91177308-0d34-0410-b5e6-96231b3b80d8