#1 Updated version of XMPPHP library

Original XMPPHP is no longer maintained. I've looked into some forks and none of them really looked ready to be adopted. Despite GS's version of XMPPHP been working with no issues (other than some, easy to fix, incompatibilities with newer versions of PHP), some commits from birkner and zorn-v forks looked interested. I've imported them and also added some optimizations of mine. From now on we better maintain this library ourselves, maybe keep an eye on those two forks.