The architecture-specific assembly versions of clone did not set errno on
failure, which is inconsistent with glibc. __clone still returns the error
via its return value, and clone is now a wrapper that sets errno as needed.
The public clone has also been moved to src/linux, as it's not directly
related to the pthreads API.
__clone is called by pthread_create, which does not report errors via
errno. Though not strictly necessary, it's nice to avoid clobbering errno
here.
based on initial work by rdp, with heavy modifications. some features
including threads are untested because qemu app-level emulation seems
to be broken and I do not have a proper system image for testing.
Bobby Bingham