Change location information for synthesized properties to be at the

property file/line rather than the @synthesize file/line. Avoids
some nasty confusing-ness with conflating the file from the scope
and the line from the original declaration.

Update a couple of testcases accordingly since I had to change
that we actually use the passed in location in EmitFunctionStart.

Fixes rdar://11026482

llvm-svn: 153714