[PECOFF] Set section characteristics based /section options.

This is a patch to let the PECOFF writer to use the information passed
by the parser for /section option. The implementation of /section should
now be complete.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@195893 91177308-0d34-0410-b5e6-96231b3b80d8