Add an option which permits the user to specify using a bitmask, that various

Add an option which permits the user to specify using a bitmask, that various
functions be compiled as mips32, without having to add attributes. This
is useful in certain situations where you don't want to have to edit the
function attributes in the source. For now it's only an option used for
the compiler developers when debugging the mips16 port.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188826 91177308-0d34-0410-b5e6-96231b3b80d8