Fix constant-time section (wrong Java method name)

[david-a-wheeler]

This fixes an error reported here: https://forum.linuxfoundation.org/discussion/866738/constant-time-algorithms-for-java by Simon (sipaynehsl).

Since I'm already there, I added C#/.NET and some links (adding the links is helpful, AND it helps everyone verify that the given answers are correct). I changed the module and method names here to Courier font; we should probably do that everywhere eventually, but so this is a start.

Thank you!