First stage of dynamic recompiler rewrite.

Basic IR generation calls C implementation of all instructions.
Backend generation implemented for x86, x86-64, ARM and ARM64.

src/codegen_ir.h

@@ -0,0 +1,5 @@
+#include "codegen_ir_defs.h"
+
+ir_data_t *codegen_ir_init();
+
+void codegen_ir_compile(ir_data_t *ir, codeblock_t *block);