E2K: added initial support of MCST Elbrus 2000 CPU architecture

Created by: r-a-sattarov

• added initial support of e2k in xrCore and Cmake

E2K (Elbrus 2000) - this is VLIW/EPIC architecture, like Intel Itanium (IA-64) architecture.

About this architecture:

• https://en.wikipedia.org/wiki/Elbrus_2000