encoding/asn1: handle ASN1's string type BMPString
This code enables handling of ASN1's string type BMPString, used in some digital signatures.
Parsing code taken from golang.org/x/crypto/pkcs12.
Change-Id: Ibeae9cf4d8ae7c18f8b5420ad9244a16e117ff6b
GitHub-Last-Rev:
694525351411f2ec3982a6bf4ac33be892ce1b12
GitHub-Pull-Request: golang/go#26690
Reviewed-on: https://go-review.googlesource.com/c/go/+/126624
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Bonventre <andybons@golang.org>