Lacking C++, this instead adds a mess of macros. With this done, all the
function-pointer-munging "_of" macros in asn1.h can also be removed.

Update-Note: A number of *really* old and unused ASN.1 macros were
removed.

Bug: chromium:785442
Change-Id: Iab260d114c7d8cdf0429759e714d91ce3f3c04b2
Reviewed-on: https://boringssl-review.googlesource.com/32106
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <alangley@gmail.com>