Anchor a type to the main module and the current receiver

Property definitions

nitc $ JavaCompilerVisitor :: anchor
	# Anchor a type to the main module and the current receiver
	fun anchor(mtype: MType): MType do
		if not mtype.need_anchor then return mtype
		return mtype.anchor_to(compiler.mainmodule, frame.as(not null).receiver)
	end
src/compiler/java_compiler.nit:813,2--817,4