Tokenize names with non-latin characters

[agreselin]

Hi :-) When a gnuplot variable or function name begins with a non-latin letter ElDoc complains: eldoc error: (error Gnuplot-tokenize: bad token beginning <some bad letter>). For instance, it raises that error when the point is after an ε in

ε(x) = 1/x
plot ε(x)

The script is valid and gnuplot renders it without any errors.

The manual says

Valid names are the same as in most programming languages: they must begin with a letter, but subsequent
characters may be letters, digits, or "_".

So I've replaced A-Za-z with [:alpha:] in the regexps of the function gnuplot-tokenize, and now ElDoc doesn't complain anymore. What do you think?