fesetround.c is a wrapper to do the arch independent argument
check (on archs where rounding mode is not stored in 2 bits
__fesetround still has to check its arguments)

on powerpc fe*except functions do not accept the extra invalid
flags of its fpscr register

the useless FENV_ACCESS pragma was removed from feupdateenv

the x87 exception summary (ES) and stack fault (SF) flags may be
spuriously cleared by feclearexcept using the fnclex instruction,
but these flags are not observable through libc hence maintaining
their state is not critical.

the sse and x87 rounding modes should be always the same,
the visible exception flags are the bitwise or of the two
fenv states (so it's enough to query the rounding mode or
raise exceptions on one fenv)

untested; may need followup-fixes.