message: [MappedHash] Fix alignment violations
  This fixes a few alignment problems pointed out by UBSan, and is
  otherwise NFC.
diff: @@ -357,21 +357,24 @@ public:
  }
  uint32_t GetHashIndex(uint32_t bucket_idx) const {
  + uint32_t result = UINT32_MAX;
  if (m_hash_indexes && bucket_idx < m_header.bucket_count)
  - return m_hash_indexes[bucket_idx];
  - return UINT32_MAX;
  + memcpy(&result, m_hash_indexes + bucket_idx, sizeof(uint32_t));
  + return result;
  }
  uint32_t GetHashValue(uint32_t hash_idx) const {
  + uint32_t result = UINT32_MAX;
  if (m_hash_values && hash_idx < m_header.hashes_count)
  - return m_hash_values[hash_idx];
  - return UINT32_MAX;
  + memcpy(&result, m_hash_values + hash_idx, sizeof(uint32_t));
  + return result;
  }
  uint32_t GetHashDataOffset(uint32_t hash_idx) const {
  + uint32_t result = UINT32_MAX;
  if (m_hash_offsets && hash_idx < m_header.hashes_count)
  - return m_hash_offsets[hash_idx];
  - return UINT32_MAX;
  + memcpy(&result, m_hash_offsets + hash_idx, sizeof(uint32_t));
  + return result;
  }
  bool Find(const char *name, Pair &pair) const {
  