The major changes are:
1) LinkerOptions has been merged into TargetInfo
2) LinkerInvocation has been merged into Driver
3) Drivers no longer convert arguments into an intermediate (core) argument 
   list, but instead create a TargetInfo object and call setter methods on 
   it. This is only how in-process linking would work. That is, you can 
   programmatically set up a TargetInfo object which controls the linking.
4) Lots of tweaks to test suite to work with driver changes
5) Add the DarwinDriver
6) I heavily doxygen commented TargetInfo.h

Things to do after this patch is committed:
a) Consider renaming TargetInfo, given its new roll. 
b) Consider pulling the list of input files out of TargetInfo. This will 
   enable in-process clients to create one TargetInfo the re-use it with 
   different input file lists.
c) Work out a way for Drivers to format the warnings and error done in 
   core linking.

llvm-svn: 178776

This actually doesn't change behavior with the current LinkerInvocation, but
it's needed when you make reading parallel.

llvm-svn: 177554

llvm-svn: 177079

llvm-svn: 174916

llvm-svn: 174273

llvm-svn: 173430

llvm-svn: 173300

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

This removes a bunch of llvm_unreachables and makes a File's mutability part of the type system.

llvm-svn: 172297

[Archive] Use a hash map to lookup symbols in archives. Increases performance of linking lua by ~6x.

llvm-svn: 172028

llvm-svn: 167871

llvm-svn: 167869

llvm-svn: 167854