Forward-port API 1.7.0 additions and stubs

These changes sort-of lift xbmc-addon-xvdr's compatibility to recent API 1.7.0 updates. 

Please note: While this PR makes XBMC-master initialise and load the addon, and connects to the XVDR server, this will - for some reason I don't understand, maybe you have an idea - crash the VDR (1.7.33) server:

    Mar 10 17:00:30 barias kernel: [19077.554849] VDR XVDR Server[23494]: segfault at 8 ip 00007f6c80908101 sp 00007f6c737fdae8 error 4 in libc-2.15.so[7f6c8087f000+1b5000]
    Mar 10 17:00:30 barias runvdr: restarting VDR

According to the backtrace (see http://pastebin.com/jqXv4E3M - "bt full") it crashes in src/xvdr/xvdrclient.c in processTIMER_Add() in the call to cTimer::Parse(buffer). I guess the format (or order) of some options retrieved at the top of that method have changed somehow, so the string passed to cTimer::Parse() is invalid. But this needs to be investigated further.

So while this PR doesn't provide a fully working solution ATM (and maybe looks like some half-assed attempt to update things ;) ), this PR might still act as a starting point for something. At least the client addon builds without errors :)