New functions

Hello,

I make an a patch, which adds 4 functions to sslinfo extension module:
1) ssl_extension_names() --- get short names of X509v3 extensions from client certificate and it's values;
2) ssl_extension_value(text) --- get value of extension from certificate (argument --- short name of extension);
3) ssl_extension_is_critical(text) --- returns true, if extension is critical and false, if is not (argument --- short name of extension).

You can view some information of certificate's extensions via those functions.

What do you think about it?