together with 58d68a1b
"ConvertURLToSystemPath->getSystemPathFromFileURL" and
28f3464a
"ConvertSystemPathToURL->getFileURLFromSystemPath," this replaces all those
Convert... functionality with direct calls to the corresponding osl::FileBase
functions.

Change-Id: I2876171cd337a5eb939d25d8cf1e0c1253ff73a7