Remove unnecessary mcode alloc pointer check.

Also fixes Illumos address space issue reported by Theo Schlossnagle.

src/lj_mcode.c

@@ -204,8 +204,8 @@ static void mcode_protect(jit_State *J, int prot)
 
 /* -- MCode area allocation ----------------------------------------------- */
 
-#if LJ_TARGET_X64
-#define mcode_validptr(p)	((p) && (uintptr_t)(p) < (uintptr_t)1<<47)
+#if LJ_64
+#define mcode_validptr(p)	(p)
 #else
 #define mcode_validptr(p)	((p) && (uintptr_t)(p) < 0xffff0000)
 #endif