(or loading a dso linked to libthr.so into process which was not
linked against threading library).
MFC r276630:
Remove interposing, fix malloc, reinstall signal handlers wrappers on
libthr load.
MFC r276681:
Avoid calling internal libc function through PLT or accessing data
though GOT.
MFC r277032:
Reduce the size of the interposing table and amount of
cancellation-handling code in the libthr.
MFC note:
r276646 ("do not erronously export 'openat' symbol from rtld") is not
applicable to stable/10 yet, since PATHFDS support was not merged.
7fe8fbec77