PT config should include full names of executable files on Windows

The Moat client implementation inside Tor Launcher uses Mozilla's Subprocess.jsm module to start the meek client. Mozilla's code requires that we pass in a full path to the program that is to be executed, but the ClientTransportPlugin meek ... line that we append to torrc-defaults does not include the .exe suffix for terminateprocess-buffer or other Windows executable files. We should add the suffixes everywhere for consistency.