Handling of case sensitive simple types

[matzipan]

In this XSD, the following type exists:

<xsd:simpleType name="yesNoType">
   <xsd:restriction base="xsd:string">
      <xsd:enumeration value="YES"/>
      <xsd:enumeration value="yes"/>
      <xsd:enumeration value="NO"/>
      <xsd:enumeration value="no"/>
   </xsd:restriction>
</xsd:simpleType>

Because xsd-parser tries to change the case of the enum label from YES to Yes and from yes to YES, they clash.

xsd-parser could try to detect such cases and keep the case.

[lkirkwood]

#162 addresses this but it is a breaking change so it might not get merged. It should fix this issue for you though.