Add feature flags and missing #includes.

These are needed to compile on some strict Linuxes.

src/video_call.c

@@ -33,6 +33,7 @@
 #include <stdbool.h>
 #include <curses.h>
 #include <string.h>
+#include <strings.h>
 #include <pthread.h>
 #include <unistd.h>
 #include <stdlib.h>