Pull up following revision(s) (requested by riastradh in ticket #507):

lib/libm/arch/aarch64/fenv.c: revision 1.5
lib/libm/arch/aarch64/fenv.c: revision 1.6

Fix fesetenv and feupdateenv.
- fesetenv is supposed to set the stored rounding mode (and stored trap
  settings, but they have no effect on any ARMv8 I know).
- feupdateenv is supposed to re-raise the exceptions that were raised
  in the environment when it was called.
XXX atf test
XXX pullup-9

Fix feraiseexcept.
- Don't touch the trap flags (though on all ARMv8 I know they have no
  effect anyway).
- Don't clear any existing raised exception flags; just add to them.
XXX atf test
XXX pullup-9

(martin)