[patch] testsuite fix for math tests on darwin

[Benjamin Kosnik]

>This was basically discussed recently:  someone (at Apple) needs to
>fix the gcc driver on Darwin so that it passes -lmx automatically
>to the linker. Ortherwise, we get nth annoying instances of the same problem.

Yes, I agree.

It looks, however, that some of this has already crept in.

less linkage.m4

  dnl Check libmx
  AC_CHECK_LIB(mx, sqrtf, libmx="-lmx")
  dnl ac_save_LIBS="$LIBS"
  LIBS="$LIBS $libmx"
 
It would be nice to have this done one way.

-benjamin