Add support for the Tagalog script

Add support for the Tagalog script

* lisp/language/philippine.el ("Tagalog"): New language environment.
Add composition rules for Tagalog.  Add sample text and input
method.
* lisp/international/fontset.el (script-representative-chars)
(setup-default-fontset): Support Tagalog.
* lisp/leim/quail/philippine.el ("tagalog"): New input method.
* lisp/loadup.el: Preload lisp/language/philippine.el.

* etc/HELLO: Add a Tagalog greeting.
* etc/NEWS: Announce the new language environment and its
input method.
(Bug#55529)