core: Avoid trivial snprintfs.

src/util.js.h

@@ -233,4 +233,13 @@ bool tf_util_is_mobile();
 */
 uint32_t tf_util_fnv32a(const void* buffer, int length, uint32_t start);
 
+/**
+** Populate a string buffer, truncating if necessary.
+** @param buffer The buffer.
+** @param size The size of the buffer.
+** @param string The value to set.
+** @return The number of bytes set, not including the NULL terminator.
+*/
+size_t tf_string_set(char* buffer, size_t size, const char* string);
+
 /** @} */