[main] Re-include pthread.h that was removed in pr #334, needs to be

here because it is used by the gcrypt macro

src/main.c

@@ -50,6 +50,7 @@
 #include <libavformat/avformat.h>
 #include <libavfilter/avfilter.h>
 
+#include <pthread.h>
 #include <gcrypt.h>
 GCRY_THREAD_OPTION_PTHREAD_IMPL;