Fix compiler warnings.

src/lib_string.c

@@ -64,7 +64,7 @@ LJLIB_ASM(string_byte)		LJLIB_REC(string_range 0)
 LJLIB_ASM(string_char)
 {
   int i, nargs = (int)(L->top - L->base);
-  char *buf = lj_str_needbuf(L, &G(L)->tmpbuf, (size_t)nargs);
+  char *buf = lj_str_needbuf(L, &G(L)->tmpbuf, (MSize)nargs);
   for (i = 1; i <= nargs; i++) {
     int32_t k = lj_lib_checkint(L, i);
     if (!checku8(k))

src/lj_cconv.h

@@ -29,7 +29,7 @@ static LJ_AINLINE uint32_t cconv_idx(CTInfo info)
   uint32_t idx = ((info >> 26) & 15u);  /* Dispatch bits. */
   lua_assert(ctype_type(info) <= CT_MAYCONVERT);
 #if LJ_64
-  idx = ((U64x(f436fff5,fff7f021) >> 4*idx) & 15u);
+  idx = ((uint32_t)(U64x(f436fff5,fff7f021) >> 4*idx) & 15u);
 #else
   idx = (((idx < 8 ? 0xfff7f021u : 0xf436fff5) >> 4*(idx & 7u)) & 15u);
 #endif