removing unsigned from mysql grammer due to bug

Signed-off-by: Dayle Rees <thepunkfan@gmail.com>

laravel/database/schema/grammars/mysql.php

@@ -143,7 +143,7 @@ class MySQL extends Grammar {
 	{
 		if ($column->type == 'integer' and $column->increment)
 		{
-			return ' UNSIGNED AUTO_INCREMENT PRIMARY KEY';
+			return ' AUTO_INCREMENT PRIMARY KEY';
 		}
 	}
 
@@ -418,4 +418,4 @@ class MySQL extends Grammar {
 		return 'BLOB';
 	}
 
-}
\ No newline at end of file
+}