Because we cannot yet bring a more recent musl to the mips and mipsel
architectures, we disable support for these constant until a cascading
update with rust-lang/rust has been done.

They are defined since Linux 3.1 but not in musl yet.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

See https://github.com/rust-lang/rust/pull/60775 .

[breaking change] PTRACE_GETFPXREGS and PTRACE_SETFPXREGS were incorrectly re-exported on arm but they are x86 specific

Both are linux-specific additions, and supported since kernel version
4.17 and 4.15, respectively.

This is necessary to set socket options on the Nintendo Switch, which uses a socket implementation directly ported from FreeBSD.

defined for 32-bit Solarish targets.  Since rust doesn't currently
support 32-bit Solarish targets, the line is both unnecessary and wrong.