Fix more -Wsign-compare warnings in heap, mips, base, etc.

test/unittests/heap/marking-unittest.cc

Index: test/unittests/heap/marking-unittest.cc
diff --git a/test/unittests/heap/marking-unittest.cc b/test/unittests/heap/marking-unittest.cc
index 23badcd4de784b117e00d7c82f343d7f9fc3cd39..074816bf1f6a20d024e0d05d9cd59d4f16c0e319 100644
--- a/test/unittests/heap/marking-unittest.cc
+++ b/test/unittests/heap/marking-unittest.cc
@@ -118,8 +118,8 @@ TEST(Marking, SetAndClearRange) {
     CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[0], 0xffffffffu << i);
     CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[1], (1u << i) - 1);
     bitmap->ClearRange(i, Bitmap::kBitsPerCell + i);
-    CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[0], 0x0);
-    CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[1], 0x0);
+    CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[0], 0x0u);
+    CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[1], 0x0u);
   }
   free(bitmap);
 }
@@ -139,7 +139,7 @@ TEST(Marking, ClearMultipleRanges) {
   bitmap->ClearRange(Bitmap::kBitsPerCell * 2 + 8,
                      Bitmap::kBitsPerCell * 2 + 16);
   bitmap->ClearRange(Bitmap::kBitsPerCell * 2 + 24, Bitmap::kBitsPerCell * 3);
-  CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[0], 0xffff);
+  CHECK_EQ(reinterpret_cast<uint32_t*>(bitmap)[0], 0xffffu);
   CHECK(bitmap->AllBitsSetInRange(0, Bitmap::kBitsPerCell / 2));
   CHECK(bitmap->AllBitsClearInRange(Bitmap::kBitsPerCell / 2,
                                     Bitmap::kBitsPerCell));