[Patch] Fortran: gfc_simplify_{cospi,sinpi} - fix for MPFR < 4.2.0 (was: [PATCH] fortran: add constant input support for trig functions with half-revolutions)

[Yuao Ma]

Hi Tobias and Harald,

I sincerely apologize for the breakage! I did test both preprocessor branches,
but I tested against the same MPFR version (4.2.2, which is the latest on Arch
Linux). Going forward, I will test against versions both above and below 4.2.0
to ensure this type of breakage doesn't happen again.

Best regards,
Yuao