fsck: don't include sys/signal.h for portability reasons

It isn't necessary to include sys/signal.h, and it's not available on
all systems.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/misc/fsck.c b/misc/fsck.c
index 13cfa57..19e0dfb 100644
--- a/misc/fsck.c
+++ b/misc/fsck.c
@@ -30,7 +30,6 @@
 #include "config.h"
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <sys/signal.h>
 #include <sys/stat.h>
 #include <limits.h>
 #include <stdio.h>