VMS: rather use a quick file comparison than DIFF

VMS DIFF tries to calculate all the differences, which is slower than
just reading the files and stopping at the first difference.  The
latter doesn't exist as a command, so the problem is solved with perl
and File::Compare (has been in core perl since very early version 5).
Reviewed-by: NViktor Dukhovni <viktor@openssl.org>

Configurations/descrip.mms.tmpl

@@ -260,10 +260,10 @@ descrip.mms : FORCE
                 < descrip.mms > descrip.mms-new
         @ OPEN/APPEND DESCRIP descrip.mms-new
         @ WRITE DESCRIP "# DO NOT DELETE THIS LINE -- make depend depends on it."
-        @ {- join("\n\t", map { "IF F\$SEARCH(\"$_\") .NES. \"\" THEN TYPE $_ /OUTPUT=DESCRIP:" } @deps); -}
+        {- join("\n\t", map { "\@ IF F\$SEARCH(\"$_\") .NES. \"\" THEN TYPE $_ /OUTPUT=DESCRIP:" } @deps); -}
         @ CLOSE DESCRIP
-        @ DIFF/OUTPUT=NLA0: descrip.mms,descrip.mms-new
-        @ IF $SEVERITY .EQ. 3 THEN RENAME descrip.mms-new descrip.mms
+        @ PIPE ( $(PERL) -e "use File::Compare qw/compare_text/; my $x = compare_text(""descrip.mms"",""descrip.mms-new""); exit(0x10000000 + ($x == 0));" || -
+                 RENAME descrip.mms-new descrip.mms )
         @ IF F$SEARCH("descrip.mms-new") .NES. "" THEN DELETE descrip.mms-new;*
         -@ SPAWN/OUTPUT=NLA0: PURGE/NOLOG descrip.mms