Single-precision float version of matherr

[Wilco Dijkstra]

Hi,

Rather than keeping it, consider just removing all support for matherr since it is
obsolete (http://man7.org/linux/man-pages/man3/matherr.3.html):

       "Note: the mechanism described in this page is no longer supported by
       glibc.  Before glibc 2.27, it had been marked as obsolete.  Since
       glibc 2.27, the mechanism has been removed altogether.  New
       applications should use the techniques described in math_error(7) and
       fenv(3).  This page documents the matherr() mechanism as an aid for
       maintaining and porting older applications."

I'm sure no embedded application uses matherr since it is a historical
System V oddity, so nobody will ever miss it. Note that the recently rewritten
math functions in newlib do not use matherr at all.

Wilco