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/lld/trunk@187541 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF][Driver] Prefer "/" over "-" as the indicator of the option.

This patch does not change the behavior of LLD, but changes the output of the
help text. We want to show the help text with Windows style indicator rather
than Unix style indicator.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@187544 91177308-0d34-0410-b5e6-96231b3b80d8