Add support for default public key digest type ctrl.

apps/openssl.cnf

diff --git a/apps/openssl.cnf b/apps/openssl.cnf
index a620b98..2995800 100644
--- a/apps/openssl.cnf
+++ b/apps/openssl.cnf
@@ -72,7 +72,7 @@
 
 default_days	= 365			# how long to certify for
 default_crl_days= 30			# how long before next CRL
-default_md	= sha1			# which md to use.
+default_md	= default		# use public key default MD
 preserve	= no			# keep passed DN ordering
 
 # A few difference way of specifying how similar the request should look