Include pthreads.h as the core doesn't use plain pthreads anymore

Original commit message from CVS:
Include pthreads.h as the core doesn't use plain pthreads anymore

sys/v4l/v4lmjpegsink_calls.c

@@ -25,6 +25,7 @@
 #include <sys/mman.h>
 #include <string.h>
 #include <errno.h>
+#include <pthread.h>
 #include "v4lmjpegsink_calls.h"
 
 /* On some systems MAP_FAILED seems to be missing */

sys/v4l/v4lsrc_calls.c

@@ -27,6 +27,7 @@
 #include <errno.h>
 #include "v4lsrc_calls.h"
 #include <sys/time.h>
+#include <pthread.h>
 
 /* number of buffers to be queued *at least* before syncing */
 #define MIN_BUFFERS_QUEUED 2