ImGui OpenGL loader is patched, and not regenerated, because the gl3w
script requires network connectivity to download the header files from
Khronos at build time.
Note that the negative glyph spacing is const here, regardless of the font
scaling. The alternative of using proportional spacing in reality does not
work as good as it sounds. With fractional scaling some of the glyphs will
no longer land on exact pixel boundaries, which results in blurry text.
Looking at the potential solutions for this problem is moot point, as with
the non-fractional scale of 2x and glyph spacing of -2, there is no longer
enough space separating some letters, which is especially visible in words
like "common" or register "xmm", where the "mm" pair becomes joined.
