Initiate a garbage collection

Property definitions

core :: gc $ Sys :: force_garbage_collection
	# Initiate a garbage collection
	fun force_garbage_collection is intern
lib/core/gc.nit:17,2--18,39

emscripten :: emscripten $ Sys :: force_garbage_collection
	redef fun force_garbage_collection `{ GC_FORCE_COLLECT(); `}
lib/emscripten/emscripten.nit:42,2--61