gnucash maint: Multiple changes pushed

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/1ef17e6e (commit)
	 via  https://github.com/Gnucash/gnucash/commit/bbb5e56e (commit)
	 via  https://github.com/Gnucash/gnucash/commit/21bd13b9 (commit)
	from  https://github.com/Gnucash/gnucash/commit/2cecc293 (commit)



commit 1ef17e6e16c3febd238fe7dc277a2ecba6f7b7c8
Author: John Ralls <jralls at ceridwen.us>
Date:   Sat Dec 17 11:11:56 2016 -0800

    Release 2.6.15

commit bbb5e56e309397384724dba4f971b9dde1a7806a
Author: John Ralls <jralls at ceridwen.us>
Date:   Sat Dec 17 10:20:50 2016 -0800

    Update AUTHORS and DOCUMENTORS.

commit 21bd13b91aec21fcc79f026519356ca0ba22e3c4
Author: John Ralls <jralls at ceridwen.us>
Date:   Sat Dec 17 09:45:21 2016 -0800

    Update Danish and Serbian translations from the Translation Project.



Summary of changes:
 AUTHORS        |  569 ++++++------
 CMakeLists.txt |    2 +-
 ChangeLog      |  264 +++++-
 DOCUMENTERS    |   46 +-
 NEWS           |   47 +
 configure.ac   |    2 +-
 po/da.po       | 2685 +++++++++++++++++++++++++++++---------------------------
 po/sr.po       |  781 ++++++++--------
 8 files changed, 2433 insertions(+), 1963 deletions(-)