Improvements to addon-prefs key search suggested by Yang Niren.
- add accent_grave.
- strip the search string.
- add numpad numbers (currently these match regular numbers).

also remove unneeded forward declarations in path_util.c


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55155 954f8c5b-7b00-dc11-b283-0030488c597c