MFC r304928:
Do not obliterate errno value in the main thread during ptrace(2) call on x86.

MFC r304931:
Follow ABI when calling __error from the ptrace(2) wrapper.

MFC r305012:
Rewrite ptrace(2) wrappers in C.

MFC r305022:
Restore the requirement of setting errno to zero before calling ptrace(2).

MFC: r278870

Unbreak sparc64 after r276630 (MFCed to stable/10 in r277317) by calling
__sparc_sigtramp_setup signal trampoline as part of the MD __sys_sigaction
again.

Submitted by: kib (initial versions)

MFC: r278870

Unbreak sparc64 after r276630 (MFCed to stable/10 in r277317) by calling
__sparc_sigtramp_setup signal trampoline as part of the MD __sys_sigaction
again.

Submitted by: kib (initial versions)