New modulefile Tcl command provide

[xdelaruelle]

It seems interesting for a modulefile to declare the sub-elements it provides. A new modulefile Tcl command provide may be introduced for this purpose.

Such feature will help to declare the interfaces a modulefile provides, or for instance the additional other software it ships

Providing items will be module name and version.

This new feature is shaped after the need expressed in the following mailing-list discussion:
https://sourceforge.net/p/modules/mailman/message/58762185/