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

These types have a p_types field, but the resolv.h
header defines p_types __p_types macro that breaks them.

Revert PR 1322

Reverts PR #1322 .

cc https://github.com/rust-lang/rust/pull/60117

Deprecate _pad field on siginfo_t

As discussed in https://github.com/rust-lang/libc/pull/1316

Fix getgrgid_r to accept gid_t.

Closes #1320.