Fix constraints handling in ddl2cpp (#437)

Constraints got interpreted as (unknown) data types.
This change should fix this most cases (simple test case added).

tests/scripts/ddl2cpp_sample_good.sql

@@ -28,12 +28,13 @@ CREATE TABLE tab_foo
 (
 	delta varchar(255),
 	_epsilon bigint,
-	`omega` double
+	`omega` double,
+        CONSTRAINT uc_delta UNIQUE (delta, _epsilon)
 );
 
 CREATE TABLE tab_bar
 (
-	alpha bigint AUTO_INCREMENT,
+	alpha bigint AUTO_INCREMENT RRIMARY_KEY,
 	beta varchar(255) NULL DEFAULT "",
 	gamma bool NOT NULL,
 	delta int