Include signal.h before sudo_exec.h since it uses sigset_t * in the

fork_pty prototype.

src/sesh.c

@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <signal.h>
 #include <unistd.h>
 #ifdef HAVE_SETLOCALE
 # include <locale.h>