- Rename to a corresponding backup file
  If the backup file already exists, attempt with "01" .. "99" suffix.

- git ignore indexed backup files too

- handle ThirdParty-VERSION properly

- handle wmake/utilbin/ location

- should the wmake/rules/* really be packed with a binary distribution?
  I think this is just left over from before.

- in .gitignore, added other common build targets to be ignored.
  Finalized the move of wmkdep etc to wmake/utilbin/

- the $WM_PROJECT_DIR/.build file is automatically updated.
  This file is (and must be) ignored by git.