This change exposes the functions needed to support arbitrary elliptic
curve groups. The Java API[1] doesn't allow a provider to only provide
certain elliptic curve groups. So if BoringSSL is an ECC provider on
Android, we probably need to support arbitrary groups because someone
out there is going to be using it for Bitcoin I'm sure.

Perhaps in time we can remove this support, but not yet.

[1] https://docs.oracle.com/javase/7/docs/api/java/security/spec/ECParameterSpec.html

Change-Id: Ic1d76de96f913c9ca33c46b451cddc08c5b93d80
Reviewed-on: https://boringssl-review.googlesource.com/4740
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

This is taken from upstream, although it originally came from us. This
will only take effect on 64-bit systems (x86-64 and aarch64).

Before:

Did 1496 ECDH P-256 operations in 1038743us (1440.2 ops/sec)
Did 2783 ECDSA P-256 signing operations in 1081006us (2574.5 ops/sec)
Did 2400 ECDSA P-256 verify operations in 1059508us (2265.2 ops/sec)

After:

Did 4147 ECDH P-256 operations in 1061723us (3905.9 ops/sec)
Did 9372 ECDSA P-256 signing operations in 1040589us (9006.4 ops/sec)
Did 4114 ECDSA P-256 verify operations in 1063478us (3868.4 ops/sec)

Change-Id: I11fabb03239cc3a7c4a97325ed4e4c97421f91a9

This saves about 6-7k of error data.

Change-Id: Ic28593d4a1f5454f00fb2399d281c351ee57fb14
Reviewed-on: https://boringssl-review.googlesource.com/3385
Reviewed-by: Adam Langley <agl@google.com>

Previously, error strings were kept in arrays for each subdirectory and
err.c would iterate over them all and insert them at init time to a hash
table.

This means that, even if you have a shared library and lots of processes
using that, each process has ~30KB of private memory from building that
hash table.

This this change, all the error strings are built into a sorted list and
are thus static data. This means that processes can share the error
information and it actually saves binary space because of all the
pointer overhead in the old scheme. Also it saves the time taken
building the hash table at startup.

This removes support for externally-supplied error string data.

Change-Id: Ifca04f335c673a048e1a3e76ff2b69c7264635be