Refactoring: rename functions of getting BOL and EOFL:

edit_bol() -> edit_buffer_get_bol()
edit_eol() -> edit_buffer_get_eol()

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
FIXFOR: Start of edit buffers refactoring.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Refactoring of functions that operate with editor buffer.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>