[OT] Clang seems to implement modules

[DypthroposTheImposter]

  I'd expect it to outperform pre-compiled headers, with PCH you 
can only add certain headers that you rarely change, since they 
all get packaged up into a single glob(sloow).  With this new 
module stuff you effectively get PCH for each module separately, 
so even files that are changed often will benefit from PCH.

  And no more dicking around with PCH and having to include 
'sdffx' everywhere etc..