Extend signature of field_group_form_process().

Problem/Motivation

The function signature of #process is (&$element, &$form_state, &$form). This allows implementing modules to alter even the complete form structure.
field_group_form_process() currently takes the first parameter only and routes it to hook_field_group_form_process_build_alter() so there is no way to access the form state in an implementation of this hook.

Proposed resolution

Extend the signature of field_group_form_process() with $form_state and $form and route both parameters to hook_field_group_form_process_build_alter().