Rename the internal "EP_Constant" bitmask to a less misleading "EP_ConstFunc".

FossilOrigin-Name: 4ef7ceced2b0000d21f7f8014384c04a0e4661d3
diff --git a/src/resolve.c b/src/resolve.c
index 3cca168..47df724 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -740,7 +740,7 @@
         }
 #endif
         if( pDef->funcFlags & SQLITE_FUNC_CONSTANT ){
-          ExprSetProperty(pExpr,EP_Constant);
+          ExprSetProperty(pExpr,EP_ConstFunc);
         }
       }
       if( is_agg && (pNC->ncFlags & NC_AllowAgg)==0 ){