Return value documentation should use <list>

[RalfKoban]

It may happen that the XML documentation of a return value contains text such as following example:

/// A value that indicates the relative order of the objects being compared. The return value has these meanings: Value Meaning Less than zero Some text here. Zero Some other text here. Greater than zero Some even other text here.

This is the content of a <list> and should therefore be changed into:

/// A value that indicates the relative order of the objects being compared.
/// The return value has these meanings:
/// <list type="table">
/// <listheader><term>Value</term><description>Meaning</description></listheader>
/// <item><term>Less than zero</term><description>Some text here.</description></item>
/// <item><term>Zero</term><description>Some other text here.</description></item>
/// <item><term>Greater than zero</term><description>Some even other text here.</description></item>
/// </list>

This allows the XML renderer to render that as a proper list: