use std.process.browse
fix Issue 9829

- getting program and arguments before calling getopt
  on the shortended args avoids the need for the '--'
  getopt separator in the first place
rdmd: Consider PATHEXT on Windows when trying to find dmd
Merge pull request #56 from CyberShadow/rdmd-fixes-20130404

rdmd: Consider PATHEXT on Windows when trying to find dmd
Merge pull request #53 from dawgfoto/useBrowse

use std.process.browse
Merge pull request #54 from dawgfoto/fix9829

fix Issue 9829