On rare occassions we need to turn an icon into a bitmap rather than
just draw it. For example, File Browser needs the bitmaps of the large
folder and file icons for use while dragging list items. This PR just
adds functions for this conversion from cached glyphs, and then uses
them to load the gSpecialFileImages "prv" icons so we no longer have
to include these in an embedded PNG file.
Pull Request: https://projects.blender.org/blender/blender/pulls/123749
983b0b6182