ID:355 - Add macros and #include and reduce number of warnings

Commit adds macros and #include in order to bring down the number of `warning:
implicit declaration of function 'X' [-Wimplicit-function-declaration]`
warnings.

lib/ipmi_user.c

@@ -29,6 +29,10 @@
  * 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 _BSD_SOURCE || \
+	(_XOPEN_SOURCE >= 500 || \
+	_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) && \
+	!(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
 
 #include <stdlib.h>
 #include <string.h>