more portable SQL types;

--- a/src/Pure/General/sql.scala	Wed Feb 08 22:38:08 2017 +0100
+++ b/src/Pure/General/sql.scala	Wed Feb 08 23:19:10 2017 +0100
@@ -50,7 +50,9 @@
     def string(name: String, strict: Boolean = true, primary_key: Boolean = false): Column[String] =
       new Column_String(name, strict, primary_key)
     def bytes(name: String, strict: Boolean = true, primary_key: Boolean = false): Column[Bytes] =
-      new Column_Bytes(name, strict, primary_key)
+      new Column_Bytes(name, strict, primary_key, "BLOB")  // SQL standard
+    def bytea(name: String, strict: Boolean = true, primary_key: Boolean = false): Column[Bytes] =
+      new Column_Bytes(name, strict, primary_key, "BYTEA")  // PostgreSQL
   }
 
   abstract class Column[+A] private[SQL](
@@ -89,14 +91,14 @@
   class Column_Long private[SQL](name: String, strict: Boolean, primary_key: Boolean)
     extends Column[Long](name, strict, primary_key)
   {
-    def sql_type: String = "INTEGER"
+    def sql_type: String = "BIGINT"
     def apply(rs: ResultSet): Long = rs.getLong(name)
   }
 
   class Column_Double private[SQL](name: String, strict: Boolean, primary_key: Boolean)
     extends Column[Double](name, strict, primary_key)
   {
-    def sql_type: String = "REAL"
+    def sql_type: String = "DOUBLE PRECISION"
     def apply(rs: ResultSet): Double = rs.getDouble(name)
   }
 
@@ -111,10 +113,10 @@
     }
   }
 
-  class Column_Bytes private[SQL](name: String, strict: Boolean, primary_key: Boolean)
+  class Column_Bytes private[SQL](
+    name: String, strict: Boolean, primary_key: Boolean, val sql_type: String)
     extends Column[Bytes](name, strict, primary_key)
   {
-    def sql_type: String = "BLOB"
     def apply(rs: ResultSet): Bytes =
     {
       val bs = rs.getBytes(name)