Windows: don't install __DECC_*.H

This adds the possibility to exclude files by regexp in util/copy.pl

Partial fix for #3254

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6303)

(cherry picked from commit 246bd8fd)