When the math library is compiled to just use bare IEEE_LIBM mode, many
public functions are just wrappers around the __ieee754 version.
Eliminate the extra function by creating a weak alias symbol for the
public name directly from the ieee754 name.
v2:
Use __weak_reference macro instead of using
'__attribute__((weak, alias' to make this code portable
to non-ELF systems.
v3:
Use __strong_reference macro instead of __weak_reference to
avoid changing the symbol in the resulting library. Make the
use of this and the un-definition of the wrapper functions
conditional on both the definition of _IEEE_LIBM and
__strong_reference so that systems without the latter will
still compile the wrapper functions and work properly.