assign escbtn and defbtn appropriately

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.

rsrc/dialogs/set-sdf.xml

@@ -1,7 +1,7 @@
 <?xml version='1.0' encoding='UTF-8' standalone='no'?>
 <!-- NOTE: This file should be updated to use relative positioning the next time it changes. -->
 <?xml-stylesheet href="dialog.xsl" type="text/xsl"?>
-<dialog defbtn='set'>
+<dialog defbtn='set' escbtn='cancel'>
 	<pict type='dlog' num='7' top='8' left='8'/>
 	<text size='large' top='8' left='50' width='200' height='17'>Edit Stuff Done</text>
 	<text top='30' left='50' width='200' height='50'>
@@ -15,6 +15,6 @@
 	<text top='145' left='8' width='100' height='16'>Value:</text>
 	<field name='val' top='143' left='110' width='80' height='16'/>
 	<text name='feedback' top='165' left='8' width='230' height='16'/>
-	<button name='exit' def-key='esc' type='regular' top='185' left='122'>Exit</button>
+	<button name='exit' type='regular' top='185' left='122'>Exit</button>
 	<button name='set' type='regular' top='185' left='187'>Set</button>
 </dialog>