Fix make_frame, introduce Vtemp_buffer_show_specifiers, cleanup doc-strings.

Fix make_frame, introduce Vtemp_buffer_show_specifiers, cleanup doc-strings.

* frame.c (make_frame): Call other_buffer_safely instead of
other_buffer.

* window.c (temp_output_buffer_show): Call display_buffer with
second argument Vtemp_buffer_show_specifiers and reset latter
immediately after the call.
(Vtemp_buffer_show_specifiers): New variable.
(auto_window_vscroll_p, next_screen_context_lines)
(Vscroll_preserve_screen_position): Remove leading asterisks from
doc-strings.