Merge pull request #68 from floitschG/static_size_assert

Use `static_assert` with newer compilers.
diff --git a/double-conversion/utils.h b/double-conversion/utils.h
index 2bd9ec4..28bb694 100644
--- a/double-conversion/utils.h
+++ b/double-conversion/utils.h
@@ -79,7 +79,8 @@
     defined(__AARCH64EL__) || defined(__aarch64__) || \
     defined(__riscv)
 #define DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS 1
-#elif defined(__mc68000__)
+#elif defined(__mc68000__) || \
+    defined(__pnacl__) || defined(__native_client__)
 #undef DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS
 #elif defined(_M_IX86) || defined(__i386__) || defined(__i386)
 #if defined(_WIN32)