Fix brokenness with spaces in file paths for Windows.

[apnadkarni]

This pull requests fixes the following cases that caused breakage on Windows:

• spaces in the path to tclprodebug
• spaces in the path to the Tcl script being debugged
• spaces in the path to the application running the script

Unix may have similar issues but the code paths are different and not addressed here. Spaces in file paths are in any case far less common on Unix.