Summary changes:
- Fixed critical ICACHE bug from one of the recent commits
- Complete preliminary SMM implemntation, SMI still PANICs but 'alwayscont' should work fine
- Correctly decode, disassemble and execute 'XCHG R8, rAX' x86-64 instruction
- Correctly decode, disassemble and execute multi-byte NOP 0F F1 opcode
- Fixed ENTER and LEAVE instructions in x86-64 mode
- Disasm SSE4 instructions
- Rename PNI->SSE3 everywhere in the code