Integrating p4_shelve from Chris Stoy.
I intend to make the following fixes/enhancements:
If you shelve a named changelist, and also have opend files in your defualt changelist, then the files in the default changelist will be submitted along with the shelve.
Opend files with the same filename, but different directories can not be shelved together
Filepaths with a space in the filename will not be shelved correctly.
A file opened for Add will left writable in the local workspace. When you un-shelve, and you have noclobber set on your client spec, you will get a "Can't clobber writable file" error.