Return a shortened version of the location with "{file}:{line_start}"

Property definitions

nitc :: java_compiler $ Location :: short_location
	# Return a shortened version of the location with `"{file}:{line_start}"`
	fun short_location: String do
		var file = self.file
		if file == null then return "<no file>:{line_start}"
		return "{file.filename.escape_to_c}:{line_start}"
	end
src/compiler/java_compiler.nit:1290,2--1295,4