mjpg-streamer: Fix musl compatibility

Signed-off-by: Ted Hess <thess@kitschensync.net>

multimedia/mjpg-streamer/patches/005-musl_compatibility.patch

@@ -0,0 +1,13 @@
+--- a/mjpg_streamer.h
++++ b/mjpg_streamer.h
+@@ -29,6 +29,10 @@
+ #define MAX_OUTPUT_PLUGINS 10
+ #define MAX_PLUGIN_ARGUMENTS 32
+ 
++#define __NEED_pthread_t
++#define __NEED_pthread_mutex_t
++#define __NEED_pthread_cond_t
++
+ #include <linux/types.h>          /* for videodev2.h */
+ #include <linux/videodev2.h>
+