Most C standard library functions are undefined if passed NULL, even
when the corresponding length is zero. This gives them (and, in turn,
all functions which call them) surprising behavior on empty arrays.
Some compilers will miscompile code due to this rule. See also
https://www.imperialviolet.org/2016/06/26/nonnull.html

Add OPENSSL_memcpy, etc., wrappers which avoid this problem.

BUG=23

Change-Id: I95f42b23e92945af0e681264fffaf578e7f8465e
Reviewed-on: https://boringssl-review.googlesource.com/12928
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

By using memcpy, GCC can already optimise things so that the compiled
code is identical on x86-64. Thus we don't need to worry about having
different versions for platforms with, and without, strict alignment.

(Thanks to Emil Mikulic.)

Change-Id: I08bc5fa9b67aa369be2dd2e29e4229fb5b5ff40c
Reviewed-on: https://boringssl-review.googlesource.com/10381
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

Also switch the EVP_CIPHER copy to cut down on how frequently we need to cast
back and forth.

BUG=22

Change-Id: I9af1e586ca27793a4ee6193bbb348cf2b28a126e
Reviewed-on: https://boringssl-review.googlesource.com/7689
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

gcm_test.cc needs to access the internal GCM symbols. This is
unfortunate because it means that they have to be marked OPENSSL_EXPORT
just for this.

To compensate, modes.h is removed and its contents copied into
crypto/modes/internal.h.

Change-Id: I1777b2ef8afd154c43417137673a28598a7ec30e
Reviewed-on: https://boringssl-review.googlesource.com/6360
Reviewed-by: Adam Langley <alangley@gmail.com>

Change-Id: If8643c7308e6c3666de4104d097458187dbe268c
Reviewed-on: https://boringssl-review.googlesource.com/6057
Reviewed-by: Adam Langley <alangley@gmail.com>

Change-Id: I2bf0144aaa8b670ff00b8e8dfe36bd4d237b9a8a
Reviewed-on: https://boringssl-review.googlesource.com/3140
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.)