perf: Make promise stack trace collection opt-in.

src/util.js.h

@@ -224,4 +224,13 @@ void tf_util_document_settings(const char* line_prefix);
 */
 bool tf_util_is_mobile();
 
+/**
+** Compute a 32-bit hash of a buffer.
+** @param buffer The data.
+** @param length The size of the buffer in bytes.
+** @param start The hash seed.
+** @return The computed hash.
+*/
+uint32_t tf_util_fnv32a(const void* buffer, int length, uint32_t start);
+
 /** @} */