Blender Git Loki

BLF: Fix for changing the DPI storing many fonts (300+)

Each dpi value stores its own set of font sizes, so while dragging the
dpi value would collect many sizes and never free.

Also change how BLF_cache_clear works,
it was freeing memory but not the OpenGL textures.

Now just free all the cache and GL textures and let drawing allocate them again as needed.