[Developers] synchronise all processors before aborting on parameter errors

[Thomas Radke]

Thomas Radke wrote:
> Okay, I will then just commit the CCTK_Barrier() in 
> CCTKi_FinaliseParamWarn().

I just did that.

It also needed a fix in PUGH's overloadable routine for CCTK_Barrier() 
so that it can be called before a grid hierarchy exists - please update 
this thorn as well. Carpet's overloadable routine was safe already.

-- 
Cheers, Thomas.