Switch math functions to use libc_errno and fix some errno and
floating point exceptions
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D145349
Properly set floating point exceptions and add more exceptional
values for non-FMA x86-64 targets.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D143699
This part of the effort to make all test related pieces into the `test`
directory. This helps is excluding test related pieces in a straight
forward manner if LLVM_INCLUDE_TESTS is OFF. Future patches will also move
the MPFR wrapper and testutils into the 'test' directory.
