[1.8.x] Fixed #24615 -- ordering by expression not part of SELECT

Fixed queries where an expression was used in order_by() but the
expression wasn't in the query's select clause (for example the
expression could be masked by .values() call)

Thanks to Trac alias MattBlack85 for the report.
Backport of fb5c7748da from master.

django/contrib/gis/db/backends/base/adapter.py

@@ -12,6 +12,9 @@ class WKTAdapter(object):
             return False
         return self.wkt == other.wkt and self.srid == other.srid
 
+    def __hash__(self):
+        return hash((self.wkt, self.srid))
+
     def __str__(self):
         return self.wkt
 

django/contrib/gis/db/backends/postgis/adapter.py

@@ -28,6 +28,9 @@ class PostGISAdapter(object):
             return False
         return (self.ewkb == other.ewkb) and (self.srid == other.srid)
 
+    def __hash__(self):
+        return hash((self.ewkb, self.srid))
+
     def __str__(self):
         return self.getquoted()