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>

Get all this stuff out of the way.

- OPENSSL_NO_MD5
- OPENSSL_NO_SHA
- OPENSSL_NO_EC
- OPENSSL_NO_ECDSA
- OPENSSL_NO_ECDH
- OPENSSL_NO_NEXTPROTONEG
- OPENSSL_NO_DH
- OPENSSL_NO_SSL3
- OPENSSL_NO_RC4
- OPENSSL_NO_RSA

Also manually removed a couple instances of OPENSSL_NO_DSA that seemed to be
confused anyway. Did some minor manual cleanup. (Removed a few now-pointless
'if (0)'s.)

Change-Id: Id540ba97ee22ff2309ab20ceb24c7eabe766d4c4
Reviewed-on: https://boringssl-review.googlesource.com/1662
Reviewed-by: Adam Langley <agl@google.com>

Change-Id: If0dbbadb33a073b4faee500fdff900a5094ec889
Signed-off-by: Piotr Sikora <piotr@cloudflare.com>
Reviewed-on: https://boringssl-review.googlesource.com/1362
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.)