Added W-exemption (for exceeding mail waiting/mailbox maximum).

text/menu/exempt.asc

 A=Anonymous         H=Inactivity        O=QWK Packet Size   V=AutoLogon Via IP
-B=                  I=Interrupt Nodes   P=Permanent         W=
+B=                  I=Interrupt Nodes   P=Permanent         W=Mail Waiting
 C=Chat Page	    J=Chat Cost 	Q=Quiet/Anon Node   X=Xtrn Program Cost
 D=Download Cost     K=                  R=Remove Files      Y=
 E=Expire by Time    L=Logons            S=NetMail Cost      Z=