keysymdef.h: add dead_hamza symbol

It is intended to be added to the ara(mac-phonetic) and my(phonetic) layouts on the <BKSL> key. They are based on the following layouts listed in the CLDR:

• https://github.com/unicode-org/cldr/blob/main/keyboards/osx/ar-t-k0-osx-qwerty.xml
• https://github.com/unicode-org/cldr/blob/main/keyboards/osx/ms-t-k0-osx.xml

In CLDR, the dead keys are defined in the <transforms> section. Hamza “ء” is used there in the first position, making it a dead key. Now, among the keys that produce this character, E02 has transform="no" while D13 has not. So hamza on D13 is a dead key but it is not on E02.

The compose sequences required for the mentioned layouts are intended to be added to libX11. Specifically, dead_hamza with alef, waw and yeh to generate hamzaonalef, hamzaonwaw, and hamzaonyeh, respectively. Additional sequences might be added as necessary.

<transforms type="simple">
	<transform from="ء\u{64E}" to="آ"/> <!--  ءَ → آ -->
	<transform from="ء\u{650}" to="إ"/> <!--  ءِ → إ -->
	<transform from="ء " to="ء"/>
	<transform from="ء\u{A0}" to="ء"/>
	<transform from="ء!" to="إ"/>
	<transform from="ء١" to="إ"/>
	<transform from="ءا" to="أ"/>
	<transform from="ءس" to="ئ"/>
	<transform from="ءو" to="ؤ"/>
	<transform from="ءي" to="ئ"/>
	<transform from="ءى" to="ئ"/>
</transforms>

Images taken from the macOS Keyboard Viewer:

Arabic:

Jawi:

An orange outline signifies a dead key.