Change how LocateDSYMInVincinityOfExecutable strips off path

components to not depend on "." characters in the fileanme
(e.g. "Foundation.framework") but instead to just use path
separators.  The names of the files themselves may have dots
in them ("com.apple.sbd") which would break the old scheme.

Also add a test case for this (macosx/find-dsym/bundle-with-dot-in-filename)
as well as a test case for r304520 (macosx/find-dsym/deep-bundle)
which needed a similar setup to test correctly on a single machine.
(both of these are really testing remote debug session situations
where the binary can't be found on the system where lldb is running,
complicating the test case a bit.)

<rdar://problem/31825940> 

llvm-svn: 305441