New program: pcapper

Runs on a node and uses libpcap to count packets going by. Opens a
socket, so that remote programs can connect and, say, graph its
output. The client gets to specify the interval at which it wants
counts reported. Supports multiple interfaces, and multiple clients
(with different intervals.) It can also write packet counts to a file,
for analysis later.

tools/pcapper/GNUmakefile

+CPPFLAGS= -D_THREAD_SAFE -DEMULAB
+CPPFLAGS_FREEBSD= $(CPPFLAGS) -I/usr/local/include/pthread/linuxthreads
+CPPFLAGS_LINUX= $(CPPFLAGS) -I/usr/include/pcap 
+#CFLAGS=-pedantic -ansi -Wall -Werror
+CFLAGS=-Wall
+LDFLAGS= -lpcap -llthread -llgcc_r -L/usr/local/lib
+
+all: pcapper
+
+clean:
+	-rm pcapper pcapper.linux
+
+pcapper: pcapper.c GNUmakefile
+	$(CC) $(CFLAGS) $(CPPFLAGS_FREEBSD) $(LDFLAGS) pcapper.c \
+		-o pcapper -lpcap
+
+pcapper.linux: pcapper.c GNUmakefile
+	$(CC) $(CFLAGS) $(CPPFLAGS_LINUX) -L/usr/lib -lpthread -lpcap \
+	pcapper.c -o pcapper.linux -lpcap