gpg: Reject signatures made with MD5.

* g10/gpg.c: Add option --allow-weak-digest-algos.
(main): Set option also in PGP2 mode.
* g10/options.h (struct opt): Add flags.allow_weak_digest_algos.
* g10/sig-check.c (do_check): Reject MD5 signatures.
* tests/openpgp/gpg.conf.tmpl: Add allow_weak_digest_algos.
--
(cherry picked from commit f90cfe6b66)

Resolved conflicts:
	g10/gpg.c - adjust.
	tests/openpgp/defs.inc - no changes

tests/openpgp/defs.inc

@@ -68,7 +68,7 @@ error () {
     defs_error_seen=yes
     echo "$pgmname:" $* >&5
     if [ x$defs_stop_on_error != xyes ]; then
-      exit 1 
+      exit 1
     fi
 }
 
@@ -189,7 +189,7 @@ pgmname=`basename $0`
 [ -z "$srcdir" ] && fatal "not called from make"
 
 # Make sure we have a valid option file even with VPATH builds.
-for f in gpg.conf ; do 
+for f in gpg.conf ; do
   if [ -f ./$f ]; then
     :
   elif [ -f $srcdir/$f.tmpl ]; then

tests/openpgp/gpg.conf.tmpl

@@ -3,3 +3,4 @@ no-secmem-warning
 no-permission-warning
 batch
 no-auto-check-trustdb
+allow-weak-digest-algos