bug#33729: 27.0.50; Partial glyphs not rendered for Gujarati with Harfbuzz enabled (renders fine using m17n)

[Paul Eggert]

Florian Beck pointed out some examples of possible related problems when 
rendering Emacs's etc/HELLO file; see:

https://lists.gnu.org/r/emacs-devel/2018-12/msg00271.html

For the names of the languages in the languages, Harfbuzz seems to be better for 
Burmese (မြန်မာ) (where master is wrong); conversely Harfbuzz seems to be wrong 
for Maldivian (ދިވެހި) (where master is better). Please see the following for 
what these should look like:

https://en.wikipedia.org/wiki/File:Dhivehiscript.svg

https://en.wikipedia.org/wiki/File:Burmese_script_sample.svg