Added notes about two recent bugfixes

RELEASE_NOTES

@@ -4,6 +4,8 @@ OpenSCAD 2012.XX
 Bugfixes:
 o use'ing an non-existing file sometimes crashed under Windows
 o Better font handling: Ensure a monospace font is chosen as default
+o Division by zero caused hang in some cases (e.g. sin(1/0))
+o Larger minkowski operations sometimes caused a crash after a CGAL assert was thrown
 
 Deprecations:
 o The old include syntax "<filename.scad>" without the include keyword is no