Add ifcounters program that displays interface counters

ifcounters/Makefile

@@ -0,0 +1,24 @@
+CC?=
+PREFIX?=/usr/local
+CPPFLAGS=-I$(PREFIX)/include
+CFLAGS=-Wall -Wextra -g -O2 -pipe -funroll-loops -ffast-math -fno-strict-aliasing
+CFLAGS+=$(CPPFLAGS)
+LDFLAGS=-L$(PREFIX)/lib
+LDLIBS=-lm
+RM?=rm -f
+
+IFCOUNTERS = ifcounters
+OBJ = ifcounters.o
+
+all: $(IFCOUNTERS)
+
+$(IFCOUNTERS): $(OBJ)
+	$(CC) $(LDFLAGS) $(OBJ) $(LDLIBS) -o $(IFCOUNTERS)
+
+install: all
+	install -s -C $(IFCOUNTERS) $(PREFIX)/bin
+
+clean:
+	$(RM) *.o *.a a.out core *.core temp.* $(IFCOUNTERS)
+	$(RM) -r *.dSYM
+