error handers in the Unicode codecs: Negative
positions are treated as being relative to the end of
the input and out of bounds positions result in an
IndexError.
Also update the PEP and include an explanation of
this in the documentation for codecs.register_error.
Fixes a small bug in iconv_codecs: if the position
from the callback is negative *add* it to the size
instead of substracting it.
From SF patch #677429.
The errors attribute can be changed after the reader/writer
is created.
For encoding there are two additional errors values:
"xmlcharrefreplace" and "backslashreplace".
These values can be extended via register_error().
BOM_UTF32, BOM_UTF32_LE and BOM_UTF32_BE that represent the Byte
Order Mark in UTF-8, UTF-16 and UTF-32 encodings for little and
big endian systems.
The old names BOM32_* and BOM64_* were off by a factor of 2.
This closes SF bug http://www.python.org/sf/555360
