required for WEXITSTATUS macro

Index: src/application.c
--- src/application.c.orig
+++ src/application.c
@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/wait.h>
 
 // Special ids for windows size and position
 #define SIZE_FULLSCREEN  SIZE_MAX
