Option parsing tables: pick up AliasArgs from the OPTION macro.

This depends on LLVM r187537.

The SUPPORT_ALIASARGS macro will be removed once all option parsing
clients have been updated.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187538 91177308-0d34-0410-b5e6-96231b3b80d8