ioping: move features macro into source code

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>

Makefile

-CFLAGS+=-std=gnu99 -g -Wall -Wextra -pedantic -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64
+CFLAGS+=-std=gnu99 -g -Wall -Wextra -pedantic
 LIBS=-lm
 PREFIX=/usr/local
 BINDIR=$(PREFIX)/bin

ioping.c

@@ -18,6 +18,9 @@
  *
  */
 
+#define _GNU_SOURCE
+#define _FILE_OFFSET_BITS 64
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>