JHT ===> Changed behaviour of logon script processing so that all macros

JHT ===> Changed behaviour of logon script processing so that all macros
         can be used in the logon script parameter definition in the smb.conf
         Globals section. This fixes a problem reported by Jacco de Leeuw
         where OS/2 does not see the %u variable. Jacco suggested using %U
         but we really do want the user for the netlogon share session.
         If this does not do the trick - well we eat our hat! Yeh!
(This used to be commit a7716b2e70606e447094509116455ea53fe8bf64)