This is portions of Andrew M.'s ed25519-donna implementing ed25519_publickey()
ported over from C (generic 32-bit code) to OpenCL by Solar Designer.  Here we
use JtR-specific memcpy_*() for copying between address spaces, which we assume
come from a previously #include'ed file before a #include of ed25519-donna.c.

The filenames of original ed25519-donna have been preserved to allow for easy
"diff -ur" against the original.

The porting to OpenCL was funded by the Tezos Foundation, and the code stays in
the public domain.
