move misc/math_extras.h to sys/math_extras.h and
create a shim for backward-compatibility.
No functional changes to the headers.
A warning in the shim can be controlled with CONFIG_COMPAT_INCLUDES.
Related to #16539
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
The implementation of the <misc/math_extras.h> functions will use the
portable C code when PORTABLE_MISC_MATH_EXTRAS is defined before
including the header.
Use this feature macro to make sure that the unit test always tests the
portable functions in addition to the ones using builtins for the
current compiler.
Signed-off-by: Jakob Olesen <jolesen@fb.com>