Part of #2080.
This change vendors `crypto/x509`, `crypto/x509/pkix`, and `encoding/asn1` from 1d5f6a765d. That commit is a direct child of the Go 1.5.4 release tag, so it contains the same code as the current Go version we are using. In that commit I rewrote imports in those packages so they depend on each other internally rather than calling out to the standard library, which would cause type disagreements.
I changed the imports in each place where we're parsing CSRs, and imported under a different name `oldx509`, both to avoid collisions and make it clear what's going on. Places that only use `x509` to parse certificates are not changed, and will use the current standard library.
This will unblock us from moving to Go 1.6, and subsequently Go 1.7.
The `regID` parameter in the PA's `WillingToIssue` function was originally used for whitelisting purposes, but is not used any longer. This PR removes it.
* Split CSR testing and name hoisting into own functions, verify CSR in RA & CA
* Move tests around and various other fixes
* 1.5.3 doesn't have the needed stringer
* Move functions to their own lib
* Remove unused imports
* Move MaxCNLength and BadSignatureAlgorithms to csr package
* Always normalizeCSR in VerifyCSR and de-export it
* Update comments
Roland Bracewell Shoemaker