* contrib/lisp/ob-vbnet.el: Add org-babel functions for VB.Net evaluation.
(org-babel-vbnet-command): Name of the VB command (mono)
(org-babel-vbnet-compiler): Name of the VB compiler (vbnc)
(org-babel-execute:vbnet): Execute VB.Net code
(org-babel-prep-session:vbnet): Throw error (sessions are not supported)
