Use memcpy() instead of violating strict-aliasing rules.

include/opentype-sanitiser.h

Index: include/opentype-sanitiser.h
===================================================================
--- include/opentype-sanitiser.h	(revision 79)
+++ include/opentype-sanitiser.h	(working copy)
@@ -57,8 +57,9 @@
     }
 
     if (chksum_buffer_offset_ == 4) {
-      // TODO(yusukes): This cast breaks the strict-aliasing rule.
-      chksum_ += ntohl(*reinterpret_cast<const uint32_t*>(chksum_buffer_));
+      uint32_t chksum;
+      std::memcpy(&chksum, chksum_buffer_, 4);
+      chksum_ += ntohl(chksum);
       chksum_buffer_offset_ = 0;
     }