Fixed test_upgrade_ssl.c: missing include for waitpid()

src/microhttpd/test_upgrade_ssl.c

@@ -29,6 +29,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 
 #ifndef WINDOWS
 #include <unistd.h>