Imports of sctcheck command

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
crypto/tlsPackage tls partially implements TLS 1.2, as specified in RFC 5246, and TLS 1.3, as specified in RFC 8446.
errorsPackage errors implements functions to manipulate errors.
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/golang/glogPackage glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup.
github.com/google/certificate-transparency-goPackage ct holds core types and utilities for Certificate Transparency.
github.com/google/certificate-transparency-go/ctutilPackage ctutil contains utilities for Certificate Transparency.
github.com/google/certificate-transparency-go/loglist
github.com/google/certificate-transparency-go/x509Package x509 parses X.509-encoded keys and certificates.
github.com/google/certificate-transparency-go/x509utilPackage x509util includes utility code for working with X.509 certificates from the x509 package.
io/ioutilPackage ioutil implements some I/O utility functions.
netPackage net provides a portable interface for network I/O, including TCP/IP, UDP, domain name resolution, and Unix domain sockets.
net/httpPackage http provides HTTP client and server implementations.
net/urlPackage url parses URLs and implements query escaping.
osPackage os provides a platform-independent interface to operating system functionality.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.
timePackage time provides functionality for measuring and displaying time.