gnucash maint: Bug 795080 - Some dates reset to 01/01/1970

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/0e723610 (commit)
	from  https://github.com/Gnucash/gnucash/commit/19b3643a (commit)



commit 0e723610f0cb23515f564bc87e6b0b2f16577f5b
Author: John Ralls <jralls at ceridwen.us>
Date:   Fri Nov 2 10:29:52 2018 -0700

    Bug 795080 - Some dates reset to 01/01/1970
    
    The first fix for this bug handled structs tm with ambiguous times.
    This one fixes the GncDate constructor when the time is ambiguous
    because it's in the DST-change hour, using the same add 3 hours,
    construct the LDT, and subtract the 3 hours from the result.
    
    The string constructor handles only simple-offset HH:MM timezones and so
    is immune to the bug.



Summary of changes:
 libgnucash/engine/gnc-datetime.cpp            | 59 +++++++++++++++++++++------
 libgnucash/engine/test/gtest-gnc-datetime.cpp | 22 ++++++++++
 po/POTFILES.in                                |  1 +
 3 files changed, 69 insertions(+), 13 deletions(-)