fenv-*: Port to Haiku

[Bruno Haible]

On Haiku/x86_64, version hrev57363 or newer, I see this test failure:

FAIL test-fenv-except-state-2 (exit status: 149)

Looking at it in the debugger, it crashes at an 'fld1' instruction, here:

  /* Do a harmless floating-point operation (since on some CPUs, floating-point
     exceptions trigger a trap only at the next floating-point operation).  */
  a = 1.0; b = a + a;                  // <==== HERE

This means, the function fesetexceptflag() triggers a floating-point
exception, although it shouldn't.

This hypothesis can be verified by rebuilding with the configure arguments
  gl_cv_func_fesetexceptflag_works1=no gl_cv_func_fesetexceptflag_works2=no

So, this patch fixes it. Likewise on Haiku/i386 (r1beta4 from 2022).


2023-11-05  Bruno Haible  <bruno@clisp.org>

        fenv-exceptions-trapping: Avoid test failure on Haiku/i386.
        * tests/test-fenv-except-trapping-2.c (main): Skip the '4' tests also on
        Haiku/i386.

        fenv-exceptions-state: Fix test failure on Haiku/i386 and Haiku/x86_64.
        * m4/fenv-exceptions-state.m4 (gl_FENV_EXCEPTIONS_STATE): Arrange to
        override fesetexceptflag() on Haiku.
        * doc/posix-functions/fesetexceptflag.texi: Mention the Haiku bug.

0001-fenv-exceptions-state-Fix-test-failure-on-Haiku-i386.patch
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0002-fenv-exceptions-trapping-Avoid-test-failure-on-Haiku.patch
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