OP_ENTER: Rewrite split aspec use macros

src/vm.c

@@ -1364,14 +1364,14 @@ RETRY_TRY_BLOCK:
       /* Ax             arg setup according to flags (23=5:5:1:5:5:1:1) */
       /* number of optional arguments times OP_JMP should follow */
       mrb_aspec ax = GETARG_Ax(i);
-      int m1 = (ax>>18)&0x1f;
-      int o  = (ax>>13)&0x1f;
-      int r  = (ax>>12)&0x1;
-      int m2 = (ax>>7)&0x1f;
+      int m1 = MRB_ASPEC_REQ(ax);
+      int o  = MRB_ASPEC_OPT(ax);
+      int r  = MRB_ASPEC_REST(ax);
+      int m2 = MRB_ASPEC_POST(ax);
       /* unused
-      int k  = (ax>>2)&0x1f;
-      int kd = (ax>>1)&0x1;
-      int b  = (ax>>0)& 0x1;
+      int k  = MRB_ASPEC_KEY(ax);
+      int kd = MRB_ASPEC_KDICT(ax);
+      int b  = MRB_ASPEC_BLOCK(ax);
       */
       int argc = mrb->c->ci->argc;
       mrb_value *argv = regs+1;