gnucash-docs maint: Release 2.6.18

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash-docs/commit/c15a2c1c (commit)
	from  https://github.com/Gnucash/gnucash-docs/commit/2cd4f41a (commit)



commit c15a2c1c72c9f6dcdcd3a738df570ea849fc40c8
Author: John Ralls <jralls at ceridwen.us>
Date:   Thu Sep 21 11:42:30 2017 -0700

    Release 2.6.18



Summary of changes:
 ChangeLog                  | 116 +++++++++++++++++++++++++++++++++++++++++++++
 NEWS                       |   8 ++++
 configure.ac               |   2 +-
 guide/C/gnucash-guide.xml  |  10 ++--
 guide/de/gnucash-guide.xml |  10 ++--
 help/C/gnucash-help.xml    |  10 ++--
 6 files changed, 140 insertions(+), 16 deletions(-)