Framebuffer and texture for dynamic resolution intermediate drawing

Property definitions

gamnit :: dynamic_resolution $ App :: dynamic_context
	# Framebuffer and texture for dynamic resolution intermediate drawing
	private fun dynamic_context: DynamicContext
	do
		var cache = dynamic_context_cache
		if cache != null then return cache

		cache = create_dynamic_context
		dynamic_context_cache = cache
		return cache
	end
lib/gamnit/dynamic_resolution.nit:161,2--170,4