vi: make buffer handling more vi-like

Vi places text affected by change/delete/yank operations into a
buffer.  The contents of such buffers can be restored with the put
commands, 'p' or 'P'.  These behave differently depending on whether
the buffer contains whole lines or partial lines.  For whole lines
the text is copied into the file on the line before (P) or after
(p) the current line.  For partial lines the text is copied before
or after the current cursor position.

Whether an operation results in whole or partial lines depends on
the command used.

BusyBox vi treats any buffer with a newline as though it contained
whole lines.  This is incorrect.  Deleting multiple words across
a line boundary results in a buffer with a newline but not having
whole lines.

Rework how buffers are handled to behave more like vi.

function                                             old     new   delta
static.text_yank                                      79      99     +20
colon                                               3092    3097      +5
edit_file                                            885     887      +2
yank_delete                                          127     112     -15
.rodata                                           105139  105101     -38
find_range                                           514     467     -47
do_cmd                                              5088    4842    -246
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/4 up/down: 27/-346)          Total: -319 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

0 files changed, 0 insertions, 0 deletions