bpo-32399: Starting with AIX6.1 there is support in libc.a for uuid (RFC4122) (#4974)

Starting with AIX6.1 there is support in libc.a for uuid (RFC4122)
This patch provides the changes needed for this integration with the OS.

On AIX the base function is uuid_create() rather than uuid_generate_time()
The AIX uuid_t typedef is more aligned to the UUID field based definition
while the Linux typedef that is more aligned with UUID bytes
(or perhaps UUID bytes_le) definitions.