MakeAngleGlyph.py draws the U+2220 ANGLE mark that gets packed into each font sheet.

The mark is two straight strokes, so it is drawn here rather than lifted out of a third font that
happens to have the glyph.  The mark instead takes its cap height, stem width and baseline offset
from the sheet it is going into, measured off that sheet's own 'H'.

GENERATED FILES

The <sheet>-angle.png files in Philosopher\ and LiberationSans\ are output, not artwork.  Don't hand
edit them; they are checked in only so a sheet can be regenerated from its .bmfc alone, without
needing Python or Pillow.  Regenerate one with:

    python MakeAngleGlyph.py ..\LiberationSans\LiberationSans-Regular-32px.fnt

which rewrites the .png beside that sheet and prints the icon= line the .bmfc needs.  Adding a new
size means running this once against the freshly generated sheet, pasting the printed line into that
sheet's .bmfc, and generating again so BMFont packs the mark in.

Requires Pillow, which the rest of the build does not -- it is only needed when the art is being
regenerated, never to build the tree or to rebuild a sheet from its .bmfc.

The script reads the sheet's .fnt and its _0.png, so run it against a sheet that already exists; it
takes proportions from the real glyphs rather than guessing them from the nominal pixel size.