External Program Pre/Post Loadable Modules

This introduces pre/post execution modules for bbs.exec_xtrn. The logic previously in xtrn_sec.js for those functions is now in prextrn.js and postxtrn.js. These handle screen clear, evals, fonts, etc. Now everywhere that launches an external program will support these features

ctrl/modopts.ini

@@ -59,6 +59,11 @@
         backup_level = 10
 
 [xtrn_sec]
+; Set to true to disable execution of prextrn.js and postxtrn.js for external programs
+; when they are running as a logon event
+  disable_pre_on_logon_event = false
+  disable_post_on_logon_event = false
+  
 ; Enable multi-column display (when more than 10 external programs in a section)
 	multicolumn = true
 ; Sort the list of external programs alphabetically by name