[PATCH 1/2] Add rounding mode suffixes to conversion declarations

Hi Tom,

Two problems with this patch:

1) The _rt? functions are only declared if cl_khr_fp64 is not defined.

2) The patch declares functions such as convert_int4_rtz(int4) which are
   not defined by OpenCL, because neither the source nor destination
   type are floating point.


Thanks, r165385.