Add utilities for converting from Host endianity to big endian and little endian formats for the va…

runtime/platform/utils.h

Index: runtime/platform/utils.h
===================================================================
--- runtime/platform/utils.h	(revision 21569)
+++ runtime/platform/utils.h	(working copy)
@@ -170,6 +170,15 @@
            length >= 0 &&
            count <= (length - offset);
   }
+
+  // Utility functions for converting values from host endianess to
+  // big or little endian values.
+  static uint16_t HostToBigEndian16(uint16_t host_value);
+  static uint32_t HostToBigEndian32(uint32_t host_value);
+  static uint64_t HostToBigEndian64(uint64_t host_value);
+  static uint16_t HostToLittleEndian16(uint16_t host_value);
+  static uint32_t HostToLittleEndian32(uint32_t host_value);
+  static uint64_t HostToLittleEndian64(uint64_t host_value);
 };
 
 }  // namespace dart