Bring syntax of role-related commands into SQL compliance. To avoid

Bring syntax of role-related commands into SQL compliance.  To avoid
syntactic conflicts, both privilege and role GRANT/REVOKE commands have
to use the same production for scanning the list of tokens that might
eventually turn out to be privileges or role names.  So, change the
existing GRANT/REVOKE code to expect a list of strings not pre-reduced
AclMode values.  Fix a couple other minor issues while at it, such as
InitializeAcl function name conflicting with a Windows system function.