Enable emitting of constant values in non-default address space as well. The APIs...

Enable emitting of constant values in non-default address space as well. The APIs emitting constants now take an additional parameter signifying the address space in which to emit. The APIs like getData8BitsDirective() etc are made virtual enabling targets to be able to define appropirate directivers for various sizes and address spaces.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63377 91177308-0d34-0410-b5e6-96231b3b80d8