DrM-i#1730: DR fails to detect path in Windows system install dir
DrM-i#1730: DR fails to detect path in Windows system install dir

- use strnicmp to check if it is Windows system install dir
- add check for 8.3 name path (i.e., progra~)
- add comment about potential problems of path check

Review-URL: https://codereview.appspot.com/269760043

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