Gnumeric 1.12.18

Andreas:
	* Improve documentation. [#733466]
	* Add warning dialog. [#733352]
	* Fix rich text roundtrip through ODF. [#737039]

Jean:
	* Fix dialogs behavior in full screen mode. [#736395]
	* Save axis format to xls. [#736656]
	* Fix recent files dialog crasher. [#737261]

Morten:
	* Fix xls export problem.  [#733771]
	* Update WEEKDAY function.
	* Fix xlsx export problem for strings.  [#736202]
	* Improve xlsx import of rich text.
	* Text suite improvements.
	* Fix minor ods rich text import problem.

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