Add implementations for the C++ standard library math (#123)

The C++ standard library, as well as generic C++ code, use [special
compiler
builtins](https://gcc.gnu.org/onlinedocs/gcc/Library-Builtins.html) to
implement math functions. Some of these have non-trivial lowerings and
are not handled in the compiler, which leads to rather opaque arcane
errors obtaining when compiling code in `--hipstdpar` mode, wherein they
end up directly consumed. This patch adds a header that forwards to the
ROCDL implementations via an uniform HIPSTDPAR interface. A
corresponding patch in the compiler will handle forwarding the builtins
that we cannot directly lower to said uniform HIPSTDPAR interface.

With this design, it is possible to provide alternative implementations,
and it is also possible for the user to provide their own
implementations if e.g. they are compiling with `-nogpuinc` and / or
`-nogpulib`.

---
🔁 Imported from
[ROCm/rocThrust#551](ROCm/rocThrust#551)
🧑‍💻 Originally authored by @AlexVlx

---------

Co-authored-by: Alex Voicu <[email protected]>
Co-authored-by: assistant-librarian[bot] <assistant-librarian[bot]@users.noreply.github.com>

Author: 2 people

projects/rocthrust/thrust/system/hip/hipstdpar/hipstdpar_lib.hpp

@@ -64,5 +64,7 @@
 #  include "impl/swap.hpp"
 #  include "impl/transformation.hpp"
 #  include "impl/uninitialized.hpp"
+// Math library implementation
+#  include "impl/math_lib.hpp"
 
 #endif