The commit adds support for move constructors and assignment to random UUID
generators and random providers. Also, in POSIX random provider, the commit
improves handling of return value from ::read(), which returns -1
in case of error and may return 0 in case of success. Retry the call when
it was interrupted before reading any bytes from /dev/urandom.
Added new tests for movability and compile-fail tests for no copyability.
This addresses GitHub issue:
https://github.com/boostorg/uuid/issues/71
