Add libuserdefs and use in cmd/{oamuser,passwd}

@@ -88,11 +88,11 @@
 $(USERDEL) :=   LIBS = $(LIBUSRGRP)
 
 $(USERMOD) :=   OBJS = $(MOD_OBJ)
 $(USERMOD) :=   LIBS = $(LIBUSRGRP)
 
-LDLIBS +=       -lbsm -lnsl -lsecdb -lproject -lzfs -ltsol
+LDLIBS +=       -luserdefs -lbsm -lnsl -lsecdb -lproject -lzfs -ltsol
 
 .PARALLEL: $(OBJECTS)
 
 all:    $(PRODUCT)