Moving meta.scm to meta-7.scm to avoid unintended override.
Addresses issue #214.

--HG--
rename : lib/meta.scm => lib/meta-7.scm
Taking a frozen copy of the initial env when we setup the meta env.
This is so that you can import into the interaction env without affecting
the (chibi) module.
Adding call-with-input-url/headers convenience utility.
Adding binary custom ports.
Adding initial web server.
Adding sexp_current_input_port(ctx) and sexp_current_output_port(ctx) macros.
Adding exception-protect.
Adding file-truncate.
Adding call-with-locked-file utility.
Fixing bug in exception-protect.
Handling reraise properly in exception-protect.
Removing call-with-locked-file for now.
Making http ports binary.
Adding bytevector support to base64 lib.
Adding bytevector support to quoted printable.
Exporting bytevector API.
Preserving binary data as bytevectors in mime parsing.
Adding port->bytevector.
Adding temporary zlib hack.
Supporting tar on bytevectors.