Sometimes we just want to see the modules of a particular directory,
not its subdirectories, so add an option to do so.
Also some minor cleanup on os.path.sep and unicode.
Test: manual
Bug: trivial
Change-Id: Ib22f515ade6c890dfe6c2bb8042c600192ae002c
Dirmods currently expects a path relative to the top of the build. If
an abs path is passed, it will never match anything.
Modify so that if path is absolute, we fix-up the path relative to
ANDROID_BUILD_TOP.
Test: manual
Bug: trivial
Change-Id: Iad99228078dc693ab5f7957e007fe1bd5cea07d2