Detect *BSDs as supporting libc as well.

Modified fastcgi server to be able to use native (and local sockets) with *BSDs as well. I tested it on FreeBSD with lighttpd & local socket and it works as expected.
Rather than starting uname, wouldn't it be better to use a native call such as in: https://github.com/mono/monodevelop/blob/7c51ae11c323d429c10acd22169373927217198f/main/src/core/Mono.Texteditor/Mono.TextEditor/Platform.cs#L48-L68