Suppose that the keyboard model is "pc105".
* gnu/installer.scm (apply-keymap): Remove model ...
* gnu/installer/newt/keymap.scm (run-keymap-page): passed here.
(run-model-page): remove procedure
* gnu/installer/record.scm (installer): Edit keymap-page prototype in comment.
* gnu/installer/keymap.scm (default-keyboard-model): New exported parameter.