Enabling online editor, while editing an xml block that uses a custom tag with mixed case defined attributes, results in an error.
Upon validation, it seems that the attribute names are converted to lowercase. This causes the validation to fail.

Steps to reproduce

Create a custom tag as such

-- in content.ini
AvailableCustomTags[]=testtag
IsInline[testtag]=true
[testtag]
CustomAttributes[]
CustomAttributes[]=attrID

-- in ezoe_attributes.ini
[CustomAttribute_testtag_attrID]
Name=attrID
Required=true

• create an article object
• add a //testtag// to the body
• disable online editor
• enable online editor
• draft saving will fail with the following error:

  Required data is either missing or is invalid:
  Summary: Attribute 'custom:attrid' is not allowed in <custom> element.
  

  (attrID attribute got converted into attrid, somehow)