[ESS] problem with file extension recognition

[Jack]

I'm using GNU emacs 20.4.1 and ESSS 5.2.5 and ESS automatically  
recognizes any .lst file as a SAS listing, and makes the buffer read  
only.  Unfortunately, most of the .lst files I edit are Oracls sql-plus  
spool files.  Is there an easy way to get ESS to not mark a .lst file  
read only unless it specifically opens it as the listing from a .sas  
file?  (I've tried some other versions of emacs and also xemacs, and  
the behavior is identical.)  I know I can toggle the 'read-only'  
attribute, but I'd rather not need to.

Thanks for any hints.