[runtime] Rename mono_thread_info_dettach () to mono_thread_info_detach ().
[System] Fixed an error in the implementation of System.Net.IPAddress.IsIPv6Teredo

The property was introduced with PR #870 but it missed to convert network byte order to host byte order, so the comparison
wasn't working correctly and the corresponding unit test failed. @marek-safar erroneously "fixed" the test in 27e07c7.

This is the corrected implementation and the original test now works as intended.
[runtime] Simplify _wapi_set_termination_details ().
Merge pull request #884 from akoeplinger/fix-ipv6-teredo

[System] Fixed an error in the implementation of System.Net.IPAddress.IsIPv6Teredo
Update Microsoft.Build.*.csproj files
Add new assembly Mono.XBuild.Utilities