[PATCH] OpenCL half support

I notice that IEEE-754-2008 does in fact define a 16-bit floating point standard now,
does your processor conform to that standard, if so there should be no objection to adding fp16 to LLVM
and you should have no problem using it, at least that’s what I think Chris is trying to say (?).

IEEE-754-2008 fp16: 1-bit sign, 5-bit exponent, 10-bit fraction

largest ~~ 2^16 (65504), smallest ~~ 2^-14 (0.000,061).

uses the same exponent interpretation as other formats
0 → +/-zero or denorm, MAX → +/-infinity or not-a-number,

and (I presume) expects IEEE round-to-nearest-even to be the default rounding mode,

-Peter Lawrence.