We want to use donna-c64 when we have a GCC with support for
64x64->uint128_t multiplying. If not, we want to use libnacl if we
can, unless it's giving us the unsafe "ref" implementation. And if
that isn't going to work, we'd like to use the
portable-and-safe-but-slow 32-bit "donna" implementation.
We might need more library searching for the correct libnacl,
especially once the next libnacl release is out -- it's likely to have
bunches of better curve25519 implementations.
I also define a set of curve25519 wrapper functions, though it really
shouldn't be necessary.
We should eventually make the -donna*.c files get build with
-fomit-frame-pointer, since that can make a difference.
The rationale for treating these files differently is that we should
be checking upstream for changes as applicable, and merging changes
upstream as warranted.
097 hasn't seen a new version since 2007; we can drop support too.
This lets us remove our built-in sha256 implementation, and some
checks for old bugs.
This gives us a few benefits:
1) make -j clean all
this will start working, as it should. It currently doesn't.
2) increased parallel build
recursive make will max out at number of files in a directory,
non-recursive make doesn't have such a limitation
3) Removal of duplicate information in make files,
less error prone
I've also slightly updated how we call AM_INIT_AUTOMAKE, as the way
that was used was not only deprecated but will be *removed* in the next
major automake release (1.13).... so probably best that we can continue
to bulid tor without requiring old automake.
(see http://www.gnu.org/software/automake/manual/html_node/Public-Macros.html )
For more reasons why, see resources such as:
http://miller.emu.id.au/pmiller/books/rmch/
