[IDEA] Redefine the PHP requirements as the official PHP password compat lib has some issues

[panique]

Currently PHP 5.3.7 is the official minimum requirement for using the PHP passwort compat library (that makes the PHP 5.5 password functions availalbe in PHP 5.3 and 5.4).

There are talks on this in the official repo, PHP 5.3.8 seems to make problems:
ircmaxell/password_compat#22

and there's a lot of discussion on the minimum PHP version, as for example Debian has merged some changes of the 5.3.7 directly into "their" PHP 5.3.3 (!!): ircmaxell/password_compat#10
which would make it possible to run the lib on DEBIAN's (!) PHP 5.3.3

We should notice that and maybe give a notice in the readme.