fix Exposé display when blur effect is enabled

Passing kCGWindowFilterDock (0x3001) to CGSAddWindowFilter worked with my
Blurminal fork and it works here. It sounds a little sketch, but no more
sketch than using any other undocumented goodness.

PTYWindow.m

@@ -103,7 +103,7 @@
     NSDictionary *optionsDict = [NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:2.0] forKey:@"inputRadius"];
     CGSSetCIFilterValuesFromDictionary(con, blurFilter, (CFDictionaryRef)optionsDict);
-    CGSAddWindowFilter(con, [self windowNumber], blurFilter, kCGWindowFilterUnderlay);
+    CGSAddWindowFilter(con, [self windowNumber], blurFilter, kCGWindowFilterDock);
 #endif
 }