port-triger: added handling for bbf plugin

added subobject porttrigger in the NAT object of tr181 datamodel.

bbf_plugin/Makefile

+LIB_PORTTRIGGER := libporttrigger.so
+
+OBJS  := nat_porttrigger.o
+
+LIB_CFLAGS = $(CFLAGS) -Wall -Werror -fstrict-aliasing
+LIB_LDFLAGS = $(LDFLAGS)
+FPIC := -fPIC
+
+.PHONY: all
+
+%.o: %.c
+	$(CC) $(LIB_CFLAGS) $(FPIC) -c -o $@ $<
+
+all: $(LIB_PORTTRIGGER)
+
+$(LIB_PORTTRIGGER): $(OBJS)
+	$(CC) $(LIB_CFLAGS) $(LIB_LDFLAGS) -shared -o $@ $^
+
+clean:
+	rm -f *.o $(LIB_PORTTRIGGER)
+