Change location information for synthesized properties to be at the

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. Use    the current scope
location as a separate parameter so that we can    match it up
better in the line table with the beginning of the scope.

Update a couple of testcases accordingly since I had to change
that we actually use the passed in location in EmitFunctionStart
and for the new metadata parameter and add a new testcase to
make sure we've got the right line numbers for synthesized
properties.

Part of rdar://11026482

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153917 91177308-0d34-0410-b5e6-96231b3b80d8