Store class tables in the image

Reduces how long it takes to load an application image.

N5 boot.art size
Before: 8007680
After: 8122368

Also reduces boot time by how long AddImageClassesToClassTable
used to take (~20ms).

Changed class hashes to be uint32_t to fix cross compilation. We need
serialized hash tables to be valid with different pointer sizes.

Bug: 22858531

Change-Id: I463fc83f499ff75f509e80c253a55b9116ee5b89
diff --git a/runtime/utf.cc b/runtime/utf.cc
index 5a11698..a2d6363 100644
--- a/runtime/utf.cc
+++ b/runtime/utf.cc
@@ -178,8 +178,8 @@
   return static_cast<int32_t>(hash);
 }
 
-size_t ComputeModifiedUtf8Hash(const char* chars) {
-  size_t hash = 0;
+uint32_t ComputeModifiedUtf8Hash(const char* chars) {
+  uint32_t hash = 0;
   while (*chars != '\0') {
     hash = hash * 31 + *chars++;
   }