SM2 encryption support both C1C3C2 and C1C2C3 cipher text splicing order, and C1C3C2 is default order.

Full Changelog: v0.5.0...v0.6.0

Full Changelog: v0.4.9...v0.5.0

Full Changelog: v0.4.8...v0.4.9

upgraded some golang 1.5 features/enhancements to smx509

1.add rfc8998 sm4 ccm/gcm test vectors
2.refactor to use internal package, avoid sm4 depends on cipher package

support xts cipher mode

fix ccm bug

support ccm mode

fix nil message issue when sm2 encryption

improve sm4 4 blocks encryption performance via reduce PINSRD instructions.