Generate warning text

Now that we're using templates, we should warn people not to edit the
resulting file.  We do it through util/dofile.pl, which is enhanced
with an option to tell what file it was called from.  We also change
the calls so the template files are on the command line instead of
being redirected through standard input.  That way, we can display
something like this (example taken from include/openssl/opensslconf.h):

    /* WARNING: do not edit! */
    /* Generated by Configure from include/openssl/opensslconf.h.in */

Reviewed-by: Rich Salz <rsalz@openssl.org>

tools/Makefile.in

@@ -59,7 +59,7 @@ clean:
 errors:
 
 c_rehash: c_rehash.in
-	$(PERL) -I$(TOP) -Mconfigdata $(TOP)/util/dofile.pl < c_rehash.in > c_rehash.new
+	$(PERL) -I$(TOP) -Mconfigdata $(TOP)/util/dofile.pl -otools/Makefile c_rehash.in > c_rehash.new
 	mv c_rehash.new c_rehash
 
 # DO NOT DELETE THIS LINE -- make depend depends on it.

tools/c_rehash.in

@@ -1,5 +1,7 @@
 #!{- $config{perl} -}
 
+# {- join("\n# ", @autowarntext) -}
+
 # Perl c_rehash script, scan all files in a directory
 # and add symbolic links to their hash values.