lineedit: print prompt and editing operations to stderr

lineedit: print prompt and editing operations to stderr

For shells, this is mandated by standards

function                                             old     new   delta
input_backward                                       215     231     +16
read_line_input                                     3015    3028     +13
draw_custom                                           66      78     +12
put_cur_glyph_and_inc_cursor                         149     159     +10
put_prompt_custom                                     47      56      +9
show_history                                          40      46      +6
input_tab                                            927     933      +6
input_delete                                         136     142      +6
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(add/remove: 0/0 grow/shrink: 8/0 up/down: 78/0)               Total: 78 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>