-time should understand multibyte encodings

[coqbot]

Note: the issue was created automatically with bugzilla2github tool

Original bug ID: BZ#3659
From: @mikeshulman
Reported version: trunk
CC: @JasonGross, @ppedrot

[coqbot]

Comment author: @mikeshulman

It appears that the snippets of code shown by the output of -time are simply a fixed number of bytes. If the cutoff happens to come in the middle of a multibyte character, weirdness ensues.

[coqbot]

Comment author: @ppedrot

That's not difficult to fix if we know what encoding we are expecting. Nonetheless, I am unsure about the fact that Coq's one encoding is or should be UTF-8.

[coqbot]

Comment author: @JasonGross

Is there any reason for picking a non-ASCII default encoding other than UTF-8?

[coqbot]

Comment author: @mikeshulman

What about using the OS default system encoding?

[coqbot]

Comment author: @ppedrot

See #609.