xmlrpc.inc: removed dl("xml.so")

This function has been deprecated and removed from php-5.3 and upwards,
and was only useful for PHP 4, which is not supported anymore.
xmlrpc.inc: remove deprecated xmlEntities
xmlrpc.inc: removed deprecated xmlrpc_backslash global
xmlrpc.inc: Converted $GLOBALS array to internal class Xmlrpc

This way $GLOBALS array won’t be polluted with internal data of
us, and if something else does something to that array, it
won’t affect us anymore.
xmlrpc.inc: changed verifyhost from 1 to 2.

New PHP versions (PHP 5.3 and so on) does not support CURL’s ssl
host checking option 1 anymore, 2 is enforced or no checks.
Renamed .inc files to .php files

.inc extension for included PHP files is not recommended, instead
standard .php should be PHP files extension.
Convert tabs to spaces.
Splitted classes from xmlrpc.php to separate files
Renamed Xmlrpc class to Phpxmlrpc
Moved Phpxmlrpc class to own file
Modernized old classes
xmlrpcmsg: Convert createPayload() from private to public

Apparently this was used elsewhere, even when it was marked as private.
Adjusting to that now...
Merge pull request #3 from Smarre/master

Modernization commits