Remove leading and trailing empty lines.

Property definitions

markdown $ MDBlock :: remove_surrounding_empty_lines
	# Remove leading and trailing empty lines.
	fun remove_surrounding_empty_lines: Bool do
		var was_empty = false
		if remove_leading_empty_lines then was_empty = true
		if remove_trailing_empty_lines then was_empty = true
		return was_empty
	end
lib/markdown/markdown.nit:1087,2--1093,4