Behaviorally: This change makes it so that Enter will never cancel
a dialog, unless that dialog only contains info to be read. Escape
will never unpredictably be treated as Enter. And some dialogs without
Escape to cancel, now can be canceled with Escape.
A lot of this just refactors dialogs to define the cancel button
at the top, not as a hotkey on a cancel button deep in the XML.
I think this makes enter/escape behavior in dialogxml files more
legible at a glance.
The text in the various help dialogs that was previously baked into an image is now drawn as text, meaning that it benefits from text unblurring when scaling is active.
This entails some small changes to layout, since it's a different font.
Dialog engine changes:
* A new picture type allowing to draw the inventory button icons directly into a dialog.
* A new widget type that simply draws a line between two points.
- Town set attitude for affecting single creature, adapted from Windows code; technically redundant, but maybe handy
- If numeric response
- Print nums (for debugging)
- SDF arithmetic - add, subtract, multiply, divide, exponentiate
- Store random to SDF (adapted from Windows code)
- Display picture (inspired by Windows code, but the implementation is completely different and totally incompatible)
