Remove internal_with_output_to_temp_buffer, replacing sole user with Lisp.

Remove internal_with_output_to_temp_buffer, replacing sole user with Lisp.

* lisp/help.el (help-form-show): New function, to be called from C.
Put help-form output in a buffer named differently than *Help*.

* src/keyboard.c (read_char): Call Lisp function help-form-show,
instead of using internal_with_output_to_temp_buffer.
(Qhelp_form_show): New var.

* src/lisp.h (internal_with_output_to_temp_buffer): Remove prototype.

* src/print.c (internal_with_output_to_temp_buffer): Function deleted.