cmd.exe 'assoc' functionality missing

Created an attachment (id=3710)
Initial implementation of assoc.

CMD.exe is missing the 'assoc', or file association command present in Windows 2000 and up. This enables a user to modify the settings that control what file types can be opened with what applications.

More details can be seen here: http://support.microsoft.com/kb/323526

According to CORE-1246 there is no other way presently (other than a registry editor) to edit file associations, and as such, this command should be useful.

Patch was tested on Windows Vista using r39998.

Current issues:

• The help string is not externalized into .rc files for translation. I'm not sure of the procedure for doing this (eg. what to put in language files for languages that I don't know, etc), but plan on learning and including in a future patch.