I really would have liked to split this patch up, but it would greatly
complicate the lld-core and lld drivers having to deal with both
{Reader,Writer}Option and TargetInfo.
llvm-svn: 173217
now Reader and Writer subclasses for each file format. Each Reader and
Writer subclass defines an "options" class which controls how that Reader
or Writer operates.
llvm-svn: 157774