Blender Git Loki

BLF: Perf: Divide by 6 the amount of verts sent to the GPU.

This means smaller imm buffer usage.

This does not reduce the number of drawcalls.

This uses geometry shader which is slow for the GPU but given we are really
CPU bound on this case, it should not matter.

A perfect implementation would:
- Set the glyph coord in a bufferTexture and just send the glyph ID to the
GPU to read the bufferTexture.
- Use GWN_draw_primitive and draw 2*strllen triangle and just retrieve the
glyph ID and color based on gl_VertexID / 6.
- Stream fixed size buffer that the Driver can discard quickly but this is
the same as improving IMM directly.