make not having check non-fatal for extra targets

Original commit message from CVS:
make not having check non-fatal for extra targets
diff --git a/Makefile.am b/Makefile.am
index 73d21e3..08d6f2e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -125,12 +125,10 @@
 	cd check && make torture
 else
 check-valgrind:
-	echo "You need to install the 'check' library"
-	exit 1
+	echo "'check' library not installed, skipping"
 
 check-torture:
-	echo "You need to install the 'check' library"
-	exit 1
+	echo "'check' library not installed, skipping"
 endif
 
 win32-update: