Bundle the non core Perl module Text::Template

Because we're using Text::Template and we know it's a non core Perl
module, we choose to bundle it into our source, for convenience.

external/perl/Downloaded.txt document what modules we choose to bundle
this way and exactly where we downloaded it from.

With this changes comes the transfer module for with_fallback.

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