Here's a "keyword" module which, in the spirit of "token.py", updates
the list of keywords automatically from a source file (in this case,
"graminit.c" seemed like a reasonable choice, easier than "Grammar/Grammar").

You get "kwlist", a sorted list of keywords; "kwdict", a dictionary
mapping each keyword to 1; and "iskeyword", a function which tells
you if a given string happens to be a keyword.