JIT: make instruction merging generic

Now it should be easier to merge more than 2-instruction-long sequences.
Also correct some minor inconsistencies in behavior between instruction
merging cases.

Source/Core/Core/PowerPC/Jit64IL/JitIL.cpp

@@ -610,16 +610,7 @@ const u8* JitIL::DoJit(u32 em_address, PPCAnalyst::CodeBuffer *code_buf, JitBloc
 		js.downcountAmount += opinfo->numCycles;
 
 		if (i == (code_block.m_num_instructions - 1))
-		{
 			js.isLastInstruction = true;
-			js.next_inst = 0;
-		}
-		else
-		{
-			// help peephole optimizations
-			js.next_inst = ops[i + 1].inst;
-			js.next_compilerPC = ops[i + 1].address;
-		}
 
 		u32 function = HLE::GetFunctionIndex(ops[i].address);
 		if (function != 0)