* lisp/language/viet-util.el (viqr-regexp): Include escaped
punctuation characters, to handle escaped punctuation correctly.
(viqr-punctuation-regexp): New defconst.
(viet-encode-viqr-region): Backslash-escape punctuation characters
matching 'viqr-punctuation-regexp' before encoding Vietnamese
characters with diacritics. (Bug#80039)
* test/lisp/language/viet-util-tests.el (viet-util-test-viqr): New
file with tests for VIQR encoding and decoding.
