Add licensing terms.

// ====================================================================

// Written by Andy Polyakov <appro@fy.chalmers.se> for the OpenSSL

// project. Rights for redistribution and usage in source and binary

// forms are granted according to the OpenSSL license.

// ====================================================================

//

// What's wrong with compiler generated code? Compiler never uses

// variable 'shr' which is pairable with 'extr'/'dep' instructions.

// Then it uses 'zxt' which is an I-type, but can be replaced with