Larger chat

This increases the maximum chat width from 150 to 300 (a little less than entire screen), because currently even the maximum width feels ridiculously cramped, to the point I find the old chat easier to read.

Also this makes the default width 150 instead of 128.

And while I'm at it, I made a few very minor cleanup in the chat code, like removing malloc calls for fixed-size strings and C has min() and max() yes yes.