codec to test all charmap codec features.
As side-effect of moving the test codec into a new module, the encodings
package codec import mechanism is checked as well.
the mapping dictionaries can now contain 1-n mappings, meaning
that character ordinals may be mapped to strings or Unicode object,
e.g. 0x0078 ('x') -> u"abc", causing the ordinal to be replaced by
the complete string or Unicode object instead of just one character.
Another feature introduced by the patch is that of mapping oridnals to
the emtpy string. This allows removing characters.
The patch is different from patch #103100 in that it does not cause a
performance hit for the normal use case of 1-1 mappings.
Written by Marc-Andre Lemburg, copyright assigned to Guido van Rossum.
Finn Bock
Tim Peters
Marc-André Lemburg