bug#46416: 27.1; syntax-propertize fails in mhtml-mode

[Leo Liu]

1. emacs -q -l test.el
2. Create a new buffer in mhtml-mode
3. Add the following two lines:

   %%var1%%
   "%%var2%%"

4. Inspect the syntax of the % char (C-u C-x =) on both lines

% in double quotes has word syntax which seems unexpected.

If we do something similar in Emacs 26 both % chars have punctuation
syntax.

test.el
Description: test.el