[CodeGen] Shrink MachineOperand by 8 bytes on Windows

Use 'unsigned' for these bitfields so they actually pack together.
Previously it used three words for these bits instead of one.

Add some static_asserts to prevent this from being undone.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323135 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed