Fixed PHP-1266: phpinfo() lists 'default' authentication mechanism

Also only list X509 if we have openssl support
Merge pull request #759 from bjori/PHP-1266-mech-list

Fixed PHP-1266: phpinfo() lists 'default' authentication mechanism

* bjori/PHP-1266-mech-list:
  Fixed PHP-1266: phpinfo() lists 'default' authentication mechanism
Fixed PHP-1267: Windows Build Failure
Rename variable to be consistent with its friends
Reduce the size of the buffer, to_read*2 seems like a good fit

Also remove unnecessary MIN() checks
Fix path to my header