This allows a specified part to be used as an alpha map (clipper) during
rendering. A dedicated vertex shader (parts.v.glsl) is introduced to
calculate clipping coordinates using an inverse transformation matrix.
Refactored parts_render_text() to use parts_render_texture() so that
alpha clipping is applied to text. This also enables color modifications
for text, while rotation and scaling remain unsupported, matching the
original PartsEngine behavior.
Incremented the parts save version since alpha_clipper_parts_no is now
persisted.
kichikuou
a5d488564a