Python3 support

[dustmop]

The last time I tried to convert makechr to python3, the performance was about 2x slower, making it an undesirable course of action. Should see if this situation has changed, or if there's some way to change the code to avoid these slowdowns.

[dustmop]

Added by ab8d3f6. Python3 is still slower, but only by about 20%. Still needs an automated test to make sure it doesn't get broken by future development, but this is good for now.