crypto/x509: ParsePKIXPublicKey parses invalid RSA public keys without errors

[szank]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   go version go1.6.2 darwin/amd64
2. What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/mgalkowski/work/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.6.2/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.6.2/libexec/pkg/tool/darwin_amd64"
GO15VENDOREXPERIMENT="1"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fno-common"
CXX="clang++"
CGO_ENABLED="1"

1. What did you do?
   If possible, provide a recipe for reproducing the error.
   A complete runnable program is good.
   A link on play.golang.org is best.
   https://play.golang.org/p/qMQ1aqX5Ox
2. What did you expect to see?
   Last line should say:
   Error parsing incorrect RSA public key
3. What did you see instead?
   INCORRECT public key have been parsed

According to
RFC3279 https://tools.ietf.org/html/rfc3279#section-2.3.1 :

The rsaEncryption OID is intended to be used in the algorithm field
of a value of type AlgorithmIdentifier.  The parameters field MUST
have ASN.1 type NULL for this algorithm identifier.

Could you please fix it ?

[szank]

I am happy to fix it myself if I find some time this weekend.

[ianlancetaylor]

CC @agl