Utilize native SQL field type declarations.

Doctrine provides a method to get the platform independent SQL field
declaration.

composer.json

@@ -19,7 +19,7 @@
         "php": ">=5.3.3"
     },
     "require-dev": {
-        "doctrine/dbal": ">=2"
+        "doctrine/dbal": ">=2.3"
     },
     "autoload": {
         "psr-0": {"Rhumsaa\\Uuid": "src/"}

src/Rhumsaa/Uuid/Doctrine/UuidType.php

@@ -36,7 +36,7 @@ class UuidType extends Type
      */
     public function getSqlDeclaration(array $fieldDeclaration, AbstractPlatform $platform)
     {
-        return $platform->getVarcharTypeDeclarationSQL($fieldDeclaration);
+        return $platform->getGuidTypeDeclartionSQL($fieldDeclaration);
     }
 
     /**