gptel: Bump version to v0.9.9

gptel.el: Bump version to v0.9.9

NEWS: Update section for 0.9.9.

gptel: Bump version to 0.9.8.5, add release date

* gptel.el: Bump version
* NEWS (0.9.8.5): Add date

gptel: Bump version to v0.9.8

* gptel.el: Update version and package description.

gptel: Bump version, require cl-lib

* gptel.el: Bump package version to 0.9.7.  Require cl-lib at
run-time -- we already do in the other gptel libraries, so it's
not worth working around it any more.  Update package commentary.

gptel: Bump version

* gptel.el: Bump version in header, improve package commentary.

gptel: Bump version

* gptel.el: Bump version to 0.9.5

gptel: Bump version

* gptel.el: Bump gptel version to 0.9.0.

gptel: Update description and bump version

gptel.el (header): Update description and bump version.

gptel: Release v0.8.5

* gptel.el: Bump version.

gptel: Make model parameters global

* gptel.el (gptel-backend, gptel-model, gptel-temperature,
gptel-max-tokens, gptel--num-messages-to-send,
gptel--system-message): Make all model/request paramters global
variables, i.e. not buffer-local by default.  This is following
the discussion in #249.

* gptel-transient.el (gptel-menu, gptel-system-prompt--setup,
gptel-system-prompt, gptel--suffix-system-message,
gptel--infix-provider, gptel--infix-temperature, gptel--switches,
gptel--set-buffer-locally, gptel--set-with-scope): and associated
transient methods: add a toggle `gptel--set-buffer-locally` to
allow model parameters to be set buffer-locally.  The function
`gptel--set-with-scope` can be used to reset a variable or set it
buffer-locally.

Reorder gptel-transient so all the custom classes, methods and
utility functions are at the top.

* README.org (all backend sections): Replace `setq-default` with
setq in the recommended configuration.