This patch allows the Mips assembler to parse and emit nested
expressions as instruction operands. It also extends the
expansion of memory instructions when an offset is given as
an expression.
Contributer: Vladimir Medic
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179657 91177308-0d34-0410-b5e6-96231b3b80d8
