Factor the AlgorithmIdentifier portions of ASN1_item_sign and ASN1_item_verify
out. This makes it possible to initialize a signature context from an
AlgorithmIdentifier without needing the data parsed into an ASN1_ITEM/void*
pair and reserialized.
Change-Id: Idc2e06b1310a3f801aa25de323d39d2b7a44ef50
Reviewed-on: https://boringssl-review.googlesource.com/1916
Reviewed-by: Adam Langley <agl@google.com>
Initial fork from f2d678e6e89b6508147086610e985d4e8416e867 (1.0.2 beta).
(This change contains substantial changes from the original and
effectively starts a new history.)
