1. Check for the presence of the private key before allocating or
   computing anything.
2. Check the return value of |BN_CTX_get|.
3. Don't bother computing the Y coordinate since it is not used.
4. Remove conditional logic in cleanup section.

Change-Id: I4d8611603363c7e5d16a8e9f1d6c3a56809f27ae
Reviewed-on: https://boringssl-review.googlesource.com/6171
Reviewed-by: Adam Langley <alangley@gmail.com>

Much of this was done automatically with
  find . -name '*.c' | xargs sed -E -i '' -e 's/(OPENSSL_PUT_ERROR\([a-zA-Z_0-9]+, )[a-zA-Z_0-9]+, ([a-zA-Z_0-9]+\);)/\1\2/'
  find . -name '*.c' | xargs sed -E -i '' -e 's/(OPENSSL_PUT_ERROR\([a-zA-Z_0-9]+, )[a-zA-Z_0-9]+,  ([a-zA-Z_0-9]+\);)/\1\2/'

BUG=468039

Change-Id: I4c75fd95dff85ab1d4a546b05e6aed1aeeb499d8
Reviewed-on: https://boringssl-review.googlesource.com/5276
Reviewed-by: Adam Langley <agl@google.com>

ECC code.

Change-Id: I1a960620edbb30e10dcbab0e8053a1deb9db3262
Reviewed-on: https://boringssl-review.googlesource.com/3402
Reviewed-by: Adam Langley <agl@google.com>

Including string.h in base.h causes any file that includes a BoringSSL
header to include string.h. Generally this wouldn't be a problem,
although string.h might slow down the compile if it wasn't otherwise
needed. However, it also causes problems for ipsec-tools in Android
because OpenSSL didn't have this behaviour.

This change removes string.h from base.h and, instead, adds it to each
.c file that requires it.

Change-Id: I5968e50b0e230fd3adf9b72dd2836e6f52d6fb37
Reviewed-on: https://boringssl-review.googlesource.com/3200
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

Removes a bit of unused code. This effectively reverts upstream's
25af7a5dbc. It's new with OpenSSL 1.0.2 so
nothing can be using it yet. We can restore it with tests if we end up wanting
it later.

(Also I think it might be misnamed. The KDF seems to be defined in X9.63, not
X9.62.)

Change-Id: I482daf681e0cf5c3bbdc72c57793f91448deaee8
Reviewed-on: https://boringssl-review.googlesource.com/2846
Reviewed-by: Adam Langley <agl@google.com>

Saves doing it ad-hoc all the time.

Change-Id: Ic1a1180f56eec37c19799649bb8f18237bd617f8
Reviewed-on: https://boringssl-review.googlesource.com/2241
Reviewed-by: Adam Langley <agl@google.com>

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)