xsdgen: Duplicate field names

[droyo]

xsdgen does not ensure struct fields for complex types are named uniquely, so generated code for a type with an attribute and element of the same name will not compile. Using a simple xsd like this:

<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://example.org/">
  <complexType name="myType2">
    <sequence>
      <element name="title" type="string"/>
      <attribute name="title" type="string"/>
    </sequence>
  </complexType>
</schema>

Generates this:

package ws

type MyType2 struct {
	Title string `xml:"title,attr"`
	Title string `xml:"http://example.org/ title"`
}

Which is not valid code. For the attribute/element case in the example, we can append "Attr" to the field name for the attribute. I can't think of other type declarations that would cause this problem, but it's something to be mindful of if we add more support for unions. The relevant portion of the XSD spec is here, I think.

[droyo]

Fixed with d363344