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/edit-text.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='okay'>
+<dialog defbtn='okay' escbtn='cancel'>
 	<field name='text' type='text' top='40' left='55' width='293' height='98'/>
 	<button name='left' type='left' top='147' left='6'/>
 	<button name='right' type='right' top='147' left='69'/>
@@ -9,6 +9,6 @@
 	<pict type='dlog' num='16' top='8' left='8'/>
 	<text size='large' top='6' left='50' width='138' height='17'>Editing text:</text>
 	<text name='num-lbl' top='8' left='197' width='100' height='14'>Text number:</text>
-	<button name='cancel' type='regular' def-key='esc' top='147' left='214'>Cancel</button>
+	<button name='cancel' type='regular' top='147' left='214'>Cancel</button>
 	<button name='okay' type='regular' top='147' left='279'>OK</button>
 </dialog>