RSP Integration

[bryanperris]

This is a tracker for incorporating the RSP into the emulator.

• Implement MIPS 4000 instructions.
• Handle halt/break commands
• Support SP DMA
• Implement the 128-bit vector unit (Cop2)
• Pass basic RSP tests
• Support the XBUS system for the RDP
• 07/07/2021: Major RSP fixes, other than some simple mistakes, load/store 'offset' operand requires clamping