Until now, (guix deprecation) had its own warning mechanism, which was
inconsistent (it did not use colors, etc.)
* guix/deprecation.scm (deprecation-warning-port): Remove
(source-properties->location-string): Remove.
(warn-about-deprecation): Use 'warning' instead of 'format'.
(define-deprecated, define-deprecated/alias): Adjust docstring.
* guix/channels.scm (build-from-source): Refer to 'guix-warning-port'
instead of 'deprecation-warning-port'.
This is a followup to b8fa86adfc.
* guix/deprecation.scm (warn-about-deprecation): Make public.
* gnu/services/base.scm (<guix-publish-configuration>)[compression]: New
field.
[compression-level]: Default to #f. Add '%' to getter name.
(guix-publish-configuration-compression-level): Define as deprecated.
(default-compression): New procedure.
(guix-publish-shepherd-service)[config->compression-options]: New
procedure.
Use 'match-record' instead of 'match'.
* doc/guix.texi (Base Services): Remove 'compression-level' and document
'compression'.
