MFC r304928:

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).

git-svn-id: svn://svn.freebsd.org/base/stable/10@305341 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f