Fix help message for new configure option --enable-debug.

The new option is --enable-debug, not --disable-debug.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/configure b/configure
index 513a0f4..14db108 100755
--- a/configure
+++ b/configure
@@ -608,7 +608,7 @@
 echo "  --static                 enable static build [$static]"
 echo "  --enable-debug-tcg       enable TCG debugging"
 echo "  --disable-debug-tcg      disable TCG debugging (default)"
-echo "  --disable-debug          enable common debug build options"
+echo "  --enable-debug           enable common debug build options"
 echo "  --enable-sparse          enable sparse checker"
 echo "  --disable-sparse         disable sparse checker (default)"
 echo "  --disable-strip          disable stripping binaries"