Fix ParseInt/ParseUint to handle explicit "0x" hex.

Also improve fastboot error reporting around max-download-size.

Change-Id: Ic3aec9460de01e5264a2803a0a6be3706d73026b
diff --git a/base/parseint_test.cpp b/base/parseint_test.cpp
index e19c6e3..8a11d29 100644
--- a/base/parseint_test.cpp
+++ b/base/parseint_test.cpp
@@ -66,3 +66,13 @@
   ASSERT_TRUE(android::base::ParseUint("0123", &u));
   ASSERT_EQ(123u, u);
 }
+
+TEST(parseint, explicit_hex) {
+  int i;
+  ASSERT_TRUE(android::base::ParseInt("0x123", &i));
+  ASSERT_EQ(0x123, i);
+
+  unsigned int u;
+  ASSERT_TRUE(android::base::ParseUint("0x123", &u));
+  ASSERT_EQ(0x123u, u);
+}