gnucash maint: Integrate Windows gzopen differences so that only one ifdef is needed.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/916caa25 (commit)
	from  https://github.com/Gnucash/gnucash/commit/f58279ab (commit)



commit 916caa25f223a36cca4a9d88ee1684ff52a777e1
Author: John Ralls <jralls at ceridwen.us>
Date:   Fri Mar 4 16:49:36 2022 -0800

    Integrate Windows gzopen differences so that only one ifdef is needed.
    
    Clarifies code.



Summary of changes:
 libgnucash/backend/xml/io-gncxml-v2.cpp | 32 +++++++++-----------------------
 1 file changed, 9 insertions(+), 23 deletions(-)