The ENGINE code had a concept of a stable-ABI for METHODs, because that
might be a useful thing in the future when people want to have blobs
that wrap PKCS#11 or something.

However, at the moment nobody uses this feature and it didn't work very
well anyway: I hadn't updated |ENGINE_free| to free them all and
|set_method| was copying the methods, but not resetting the |is_static|
flag.

This change removes support for non-static methods. We can always put it
back later if we need.

Change-Id: Ic7401c8cb1cadd46b26a215f85bc48562efe9919
Reviewed-on: https://boringssl-review.googlesource.com/3300
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>

Implementations of ENGINEs often don't want to implement every function.
This change adds an error code for those situations.

Change-Id: Id6b7eace36d06ffad7f347f556d942d447d8a2fd
Reviewed-on: https://boringssl-review.googlesource.com/1920
Reviewed-by: Wan-Teh Chang <wtc@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

Otherwise, in C, it becomes a K&R function declaration which doesn't actually
type-check the number of arguments.

Change-Id: I0731a9fefca46fb1c266bfb1c33d464cf451a22e
Reviewed-on: https://boringssl-review.googlesource.com/1582
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.)