Freeciv

As noted in #765941-11:

The client_option_adjust_defaults() mechanism for dynamic, client-specific defaults is only used by the Gtk clients, to adapt to screen size. In that context, it runs too early; it runs from client_main() calling options_load() before any other GUI-specific code has run.

• gtk_init() not called, so the screen size probing doesn't return a definite result and no adjustment is made
• GUI-specific option -- --resolution not yet parsed, so that can't affect adjustment either

Patch will remove this client-independent mechanism, and for Gtk call the existing adjustments around the same time as option migration, which is late enough to avoid the above problems. This will make the first-run adjustments work a lot more of the time.