bpo-21474: Update word/identifier definition from ascii to unicode.

In text and entry boxes, this affects selection by double-click,

movement left/right by control-left/right, and deletion left/right

by control-BACKSPACE/DEL.

bpo-33204: Consistently color invalid string prefixes.

A 'u' string prefix cannot be paired with either 'r' or 'f'.

IDLE now consistently colors as much of the prefix, starting at the

right, as is valid. Revise and extend colorizer test.

bpo-32984: Set __file__ while running a startup file.

Like Python, IDLE optionally runs 1 startup file in the Shell window

before presenting the first interactive input prompt. For IDLE,

option -s runs a file named in environmental variable IDLESTARTUP or

PYTHONSTARTUP; -r file runs file. Python sets __file__ to the startup

file name before running the file and unsets it before the first

prompt. IDLE now does the same when run normally, without the -n

option.

bpo-32940: Replace StringTranslatePseudoMapping with faster code.