Allow VC++ to be used as alternative to GCC for building in the WIN32 target.

TODOs:
- Update README
- Add dependency handling
- Add rtimersupport

cpu/native/rtimer-arch.c

@@ -39,7 +39,9 @@
  */
 
 #include <signal.h>
+#ifndef _WIN32
 #include <sys/time.h>
+#endif /* !_WIN32 */
 #include <stddef.h>
 
 #include "sys/rtimer.h"
@@ -64,12 +66,15 @@ interrupt(int sig)
 void
 rtimer_arch_init(void)
 {
+#ifndef _WIN32
   signal(SIGALRM, interrupt);
+#endif /* !_WIN32 */
 }
 /*---------------------------------------------------------------------------*/
 void
 rtimer_arch_schedule(rtimer_clock_t t)
 {
+#ifndef _WIN32
   struct itimerval val;
   rtimer_clock_t c;
 
@@ -83,5 +88,6 @@ rtimer_arch_schedule(rtimer_clock_t t)
 
   val.it_interval.tv_sec = val.it_interval.tv_usec = 0;
   setitimer(ITIMER_REAL, &val, NULL);
+#endif /* !_WIN32 */
 }
 /*---------------------------------------------------------------------------*/