Relax builtin precision tests, fix issue in div rounding

Relax builtin precision tests, fix issue in div rounding

 * sin(), cos() and derived: Use |x| * 2^-10 for mediump inputs outside
of range [-pi,pi].

 * asin(), acos(), and atan(): Use 4096 ULP for highp (from OpenCL's
fast relaxed math).

 * modf(): allow any value, including NaN, as fractional if Inf support
is not mandated for the precision (lowp and mediump).

 * atan(y, x): allow any value if y or x is Inf and no Inf support is
mandated for the precision.

 * div (and derived): allow rounding of -/+inf to -/+maxval when both
inputs are ordinary and denominator is not 0 (legal in RTZ mode).

Bug: 20453754
Bug: 18323265
Change-Id: I8e2fad8909e29993e961d66a175963071ea2e5a8