gnucash maint: Sorting speed-up: Cache the bool value of Transaction's is_closing property.

[Christian Stimming]

Updated	 via  https://github.com/Gnucash/gnucash/commit/eb9e45bc (commit)
	from  https://github.com/Gnucash/gnucash/commit/1eed3db5 (commit)



commit eb9e45bc20531f936881d2433053716473b37828
Author: Christian Stimming <christian at cstimming.de>
Date:   Mon Dec 31 14:48:26 2018 +0100

    Sorting speed-up: Cache the bool value of Transaction's is_closing property.
    
    This value is queried on each comparison of split or txn sort function,
    which means it is called quite a lot. Avoiding the KVP lookup of this
    property gains a lot in terms of CPU cycles.



Summary of changes:
 libgnucash/engine/Transaction.c  | 23 ++++++++++++++++++-----
 libgnucash/engine/TransactionP.h |  5 +++++
 2 files changed, 23 insertions(+), 5 deletions(-)