gnucash maint: Multiple changes pushed

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/af1bc450 (commit)
	 via  https://github.com/Gnucash/gnucash/commit/23f25d74 (commit)
	from  https://github.com/Gnucash/gnucash/commit/ff76db28 (commit)



commit af1bc45021aaa9c844a9e204ead402f155835e36
Author: John Ralls <jralls at ceridwen.us>
Date:   Sun Nov 19 09:36:44 2017 -0800

    A better way to handle MySQL's 0000-00-00 invalid date indicator.

commit 23f25d74d99c4f2b1b2371e1824fde93ef8127b4
Author: John Ralls <jralls at ceridwen.us>
Date:   Sun Nov 19 09:35:08 2017 -0800

    Don't try to unref a NULL GDateTime*.



Summary of changes:
 src/backend/sql/gnc-backend-sql.c   | 43 ++++++++++++++++-------
 src/libqof/qof/gnc-date.c           | 31 ++++++-----------
 src/libqof/qof/gnc-date.h           |  5 ++-
 src/libqof/qof/test/test-gnc-date.c | 68 +++++++++++++++++++++----------------
 4 files changed, 80 insertions(+), 67 deletions(-)