Enable debug build by default, for better dev testing.

In particular this may hopefully give better detection of latent
spinlock bugs.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

Config.mk

@@ -1,7 +1,7 @@
 # -*- mode: Makefile; -*-
 
 # A debug build of Xen and tools?
-debug ?= n
+debug ?= y ## TEMPORARILY ENABLED
 
 XEN_COMPILE_ARCH    ?= $(shell uname -m | sed -e s/i.86/x86_32/ \
                          -e s/i86pc/x86_32/ -e s/amd64/x86_64/)