Optional parsing of UTF entities.

[yquemener]

So this ended up impacting more files than my previous PR proposal, but I feel in a lighter way as it just proposes an optional parsing at the beginning of on_receive_fields(...) functions. It adds an optional dependency to a mod that is basically one function, utfparse.parse(text), that I will probably need to use a lot until Irrlicht's UI is fixed.

If you don't like adding a dependency, I can just add the function in a file but it will need to be repeated in each mod that provides on_receive_fields(...) functions.

[pyrollo]

Hi,

I did not find a proper way to test your PR. Can you provide a example of what to enter in formspec in order to display wanted chars ?

I tried a copy paste from google translate but it uses the "\u" form which is not parsed. Or actually behaves quite strangely: if I put "\u6e2c", signs displays "\u6e2c". But if I reopen the formspec, the "" is gone, only "u6e2c" is left.

[yquemener]

Sorry about that. Here is a sample string:
日本語

It should display as 日本語

Another one:
ça c'est l'été!

Should show as
ça c'est l'été!

You can generate such string with that tool:
https://github.com/yquemener/utfparse/blob/master/tools/UnicodeConverter.pyw

In order to display Japanese characters correctly instead of the blank rectangle characters, you also need a Japanese font like this one: https://github.com/yquemener/font_jp_noto, and to select the appropriate font in the sign formspec.