Fix cross reference table generator.

If the hash or public key algorithm is "undef" the signature type
will receive special handling and shouldn't be included in the
cross reference table.
Reviewed-by: Tim Hudson <tjh@openssl.org>

(cherry picked from commit 55f7fb88)

crypto/objects/obj_xref.h

@@ -53,9 +53,6 @@ static const nid_triple sigoid_srt[] =
 
 static const nid_triple * const sigoid_srt_xref[] =
 	{
-	&sigoid_srt[29],
-	&sigoid_srt[17],
-	&sigoid_srt[18],
 	&sigoid_srt[0],
 	&sigoid_srt[1],
 	&sigoid_srt[7],

crypto/objects/objxref.pl

@@ -91,7 +91,10 @@ EOF
 
 foreach (@srt2)
 	{
-	my $x = $xref_tbl{$_}[2];
+	my ($p1, $p2, $x) = @{$xref_tbl{$_}};
+	# If digest or signature algorithm is "undef" then the algorithm
+	# needs special handling and is excluded from the cross reference table.
+	next if $p1 eq "undef" || $p2 eq "undef";
 	print "\t\&sigoid_srt\[$x\],\n";
 	}