put the public function createReaderPECOFF() in the lld namespace and everything else in is own namespace

llvm-svn: 158135

llvm-svn: 158134

llvm-svn: 158133

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