Correct the dates for BSDCan 2012 according to [1] and [2].

There has not been an official announcement yet, though.
I also used four days (two days of tutorials and two for the actual
conference) for the dates and not five which seems to have been
used in the past.

[1] http://www.bsdcan.org/2012/
[2] http://twitter.com/#!/bsdcan/statuses/149952177941655553

share/sgml/events2012.xml

@@ -10,7 +10,7 @@
 <events>
   <cvs:keywords xmlns:cvs="http://www.FreeBSD.org/XML/CVS" version="1.0">
     <cvs:keyword name="freebsd">
-      $FreeBSD$
+      $FreeBSD: www/share/sgml/events2012.xml,v 1.1 2011/08/05 16:55:23 hrs Exp $
     </cvs:keyword>
   </cvs:keywords>
 
@@ -20,12 +20,12 @@
     <startdate>
       <year>2012</year>
       <month>5</month>
-      <day>15</day>
+      <day>9</day>
     </startdate>
     <enddate>
       <year>2012</year>
       <month>5</month>
-      <day>18</day>
+      <day>12</day>
     </enddate>
     <location>
       <country code="CA">Canada</country>