Fix pre-receive hook, arguments from stdin

I tried that hook and it got php notices, resulting the "syntax checker hook mal functionning"

I fixed it by using "php://stdin" instead of $_SERVER['argv'] 

    remote: PHP Notice:  Undefined offset: 1 in /home/michael/git/test/test-hooks/depot-bare.git/hooks/pre-receive on line 78
    remote: PHP Notice:  Undefined offset: 2 in /home/michael/git/test/test-hooks/depot-bare.git/hooks/pre-receive on line 79
    remote: PHP Notice:  Undefined offset: 3 in /home/michael/git/test/test-hooks/depot-bare.git/hooks/pre-receive on line 80