ID:354 - forcefully switch to C99 and more strict CFLAGS

Commit changes CFLAGS which include C99 and more strict flags. Watch out for
falling rocks.

lib/ipmi_main.c

@@ -29,6 +29,7 @@
  * LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
  * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
  */
+#define _XOPEN_SOURCE 700
 
 #include <stdlib.h>
 #include <stdio.h>