- unify per-version cases into a single sequence
- make use of get_register_name() for the destination register
- ignore destination write mask - it's only allowed on 2.0+ shaders,
  and only the default mask is allowed there (xyzw)
- enable swizzle on texld 1.4 (it works together with dw/dz modifiers)
- implement for shaders 2.0-3.0

- add missing GL type and make GL cfg entries for A16B16G16R16
- correct L16 type to UNSIGNED_SHORT (..16 = short, not byte)
- change internal format for X8R8G8B8 from GL_RGB to GL_RGB8 which
  seems more correct

Based on a patch by qingdoa daoo.

Set defaults similar to Win XP for Kashida and set the default char in
ScriptGetFontProperties.

Also make sure the debug registers are properly copied to the context
when set.