Fix issue when compiling with gcc 4.6.

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 6a43c77228c217e0170a00b2dc17cb7c11240af5..1c9e3a682446beed63760035f1c9673f35bc96ae 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -1435,7 +1435,7 @@ void CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, size_t chars) {
 
 
 void CopyCharsUnsigned(uint16_t* dest, const uint8_t* src, size_t chars) {
-  if (chars >= kMinComplexConvertMemCopy) {
+  if (chars >= static_cast<size_t>(kMinComplexConvertMemCopy)) {
     MemCopyUint16Uint8(dest, src, chars);
   } else {
     MemCopyUint16Uint8Wrapper(dest, src, chars);