This patch adds a set of randomized conformance tests for
double-precision math functions.
The functions included in this set were selected based on the following
criteria:
- An implementation exists in `libc/src/math/generic` (i.e., it is not
just a wrapper around a compiler built-in).
- The corresponding LLVM CPU libm implementation is correctly rounded.
- The function is listed in Table 68 of the OpenCL C Specification
v3.0.19.
