The header file was already properly located. The previous need for it
in Support had to do with the version string printing which was fixed in
r135757.

Also update build dependencies where libraries that needed the
functionality of the Target library (in the form of the TargetRegistry)
were picking it up via Support. This is pretty pervasive, essentially
every TargetInfo library (ARMInfo, etc) uses TargetRegistry, making it
depend on Target. All of these were previously just sneaking by.

llvm-svn: 135760