iproute2: fix build failure on sparc due to -Wformat and tv_usec

tv_usec is "suseconds_t" which is apparently usually
a signed long, but sometimes not....
Change the printf modifier to use signed and
cast the tv_usec to long in case it's not already long.

gcc -Wall -Wstrict-prototypes -Werror -Wmissing-prototypes -Wmissing-declarations -Wold-style-definition -O2 -I../include -DRESOLVE_HOSTNAMES -DLIBDIR=\"/usr/lib\" -DCONFDIR=\"/etc/iproute2\" -D_GNU_SOURCE -fPIC   -c -o utils.o utils.c
utils.c: In function 'print_timestamp':
utils.c:802:2: error: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type '__suseconds_t' [-Werror=format]
cc1: all warnings being treated as errors
Signed-off-by: Andreas Henriksson <andreas@fatal.se>

lib/utils.c

@@ -799,7 +799,7 @@ int print_timestamp(FILE *fp)
 
 	tstr = asctime(localtime(&tv.tv_sec));
 	tstr[strlen(tstr)-1] = 0;
-	fprintf(fp, "Timestamp: %s %lu usec\n", tstr, tv.tv_usec);
+	fprintf(fp, "Timestamp: %s %ld usec\n", tstr, (long)tv.tv_usec);
 	return 0;
 }