MINOR: spoe: Add support for pipelining/async capabilities in the SPOA example

Now, we can use the option '-c' to enable the support of a capability. By
default, all capabilities are disabled. For example:

  $> ./spoa -c async -c pipelining

In addition, it is also possible to set the maximum frame size supported by your
agent (-m) and to add a delay in frames processing (-t).

contrib/spoa_example/Makefile

@@ -6,13 +6,15 @@ CC = gcc
 LD = $(CC)
 
 CFLAGS  = -g -O2 -Wall -Werror -pthread
-LDFLAGS = -lpthread
+LDFLAGS = -lpthread  -levent -levent_pthreads
+INCS += -I../../include
+LIBS =
 
 OBJS = spoa.o
 
 
 spoa: $(OBJS)
-	$(LD) $(LDFLAGS) -o $@ $^
+	$(LD) $(LDFLAGS) $(LIBS) -o $@ $^
 
 install: spoa
 	install spoa $(DESTDIR)$(BINDIR)
@@ -21,4 +23,4 @@ clean:
 	rm -f spoa $(OBJS)
 
 %.o:	%.c
-	$(CC) $(CFLAGS) -c -o $@ $<
+	$(CC) $(CFLAGS) $(INCS) -c -o $@ $<