Part of this was to upgrade to the .NET Framework 4.6.1 to get native support for the newer TLS versions. You can get the .NET Framework 4.6.1 installer from https://www.microsoft.com/en-us/download/details.aspx?id=49981. Note that it does need to be 4.6.1, the 4.6 installer won't work.
Without this version you are likely to get an error like the following when attempting to login:
UNSUPPORTED_CLIENT: TLS 1.0 has been disabled in this organization. Please use TLS 1.1 or higher when connecting to Salesforce using https.
Other notable changes:
- Update ApexLog parsing to allow for Spring '16 date formats
- Wsdl2Apex: Add basic WSDL schema validation and reporting via error messages. Detect potential WSDL 1.1 structure issues.
- Wsdl2Apex: Apex variable names can't start with an underscore. Will be prefixed with 'x'