Copy-On-Write flag

If the Buffer was to_s'd, the next in-place altering operation will cause the current Buffer to be re-allocated.

The flag will then be set at false.

Property definitions

core $ Buffer :: written=
	# Copy-On-Write flag
	#
	# If the `Buffer` was to_s'd, the next in-place altering
	# operation will cause the current `Buffer` to be re-allocated.
	#
	# The flag will then be set at `false`.
	protected var written = false
lib/core/text/abstract_text.nit:1537,2--1543,30