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>

According to X6.90 null, object identifier, boolean, integer and enumerated
types can only have primitive encodings: return an error if any of
these are received with a constructed encoding.

(Imported from upstream's 89f40f369f414b52e00f7230b0e3ce99e430a508.)

Change-Id: Ia5d15eef72e379119f50fdbac4e92c4761bf5eaf
Reviewed-on: https://boringssl-review.googlesource.com/2835
Reviewed-by: Adam Langley <agl@google.com>

Appease clang scan-build a bit. I'm not sure it's actually worth silencing all
of them because some of them look like preserving invariants between local
variables, but some are clearly pointless or can be restructured slightly.

Change-Id: I0bc81e2589bb402ff3ef0182d7a8921e31b85052
Reviewed-on: https://boringssl-review.googlesource.com/2205
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.)