stage0 新增内存复制指令 重构vm交互

stage0/spl_mcode.h

@@ -97,6 +97,7 @@ typedef enum {
     /* 间接内存访问 */ \
     X(SPL_LOAD,      "load",        0,    1,   1,   "load sizeof(type)-bits zero-extended") \
     X(SPL_STORE,     "store",       0,    2,   0,   "store low sizeof(type)-bits") \
+    X(SPL_MEMCPY,    "memcpy",      0,    3,   0,   "copy n bytes: pop dst, src, n (VM address space)") \
     /* 原生接口 */ \
     X(SPL_NCALL,     "ncall",       1,    0,   1,   "call native function by index") \
     X(SPL_NLIB,      "nlib",        1,    0,   0,   "dlopen library (name idx)") \