add a new modified 64bit sandbox "box"

The original file was pulled from moe (git://git.ucw.cz/moe.git)
by Martin Mares's commit on Sun Jul 29 23:53:56 2012 +0200.

The modification is to make it separately compilable and to add more option
to specify additional argument to the program. (Please see usage guide.)

run `gcc -o box -std=c99 box64-new.c` to compile.

I am not sure if this new box won't break anything, so I chose to add instead of replace `box64.cc`. Beside, this one is c not c++. 

However, this is the one deployed on my production sites running Ubuntu 14.04 and on my test site running OpenSUSE 13.1. It have been working fine since 3 months ago.