Add bitwise xor support to SQLite

Fixes #1690

Author: fredericDelaporte

src/NHibernate.Test/TestCase.cs

@@ -447,14 +447,6 @@ protected DateTime RoundForDialect(DateTime value)
 				{"locate", new HashSet<System.Type> {typeof (SQLiteDialect)}},
 				{"bit_length", new HashSet<System.Type> {typeof (SQLiteDialect)}},
 				{"extract", new HashSet<System.Type> {typeof (SQLiteDialect)}},
-				{
-					"bxor",
-					new HashSet<System.Type>
-					{
-						// Could be supported like Oracle, with a template
-						typeof (SQLiteDialect)
-					}
-				},
 				{
 					"nullif",
 					new HashSet<System.Type>

src/NHibernate/Dialect/SQLiteDialect.cs

@@ -88,6 +88,10 @@ protected virtual void RegisterFunctions()
 
 			RegisterFunction("round", new StandardSQLFunction("round"));
 
+			// SQLite has no built-in support of bitwise xor, but can emulate it.
+			// http://sqlite.1065341.n5.nabble.com/XOR-operator-td98004.html
+			RegisterFunction("bxor", new SQLFunctionTemplate(null, "((?1 | ?2) - (?1 & ?2))"));
+
 			// NH-3787: SQLite requires the cast in SQL too for not defaulting to string.
 			RegisterFunction("transparentcast", new CastFunction());
 		}