siunitx deps

[Joseph Wright]

Hello all,

Prompted by other thread,s I checked the current deps listed for 
siunitx: l3kernel and l3packages. As siunitx depends on a well-setup 
LaTeX, and the latter now requires l3kernel, this can go from siunitx. 
Similarly, l3packages can be dropped as the kernel now incorporates 
xparse-like functionality.

I'd therefore suggest listing no deps at all for siunitx: yes, it relies 
on LaTeX, but I think that can be taken as read :)

Joseph