gnucash maint: [gnc-features.cpp] convert to cpp

[Christopher Lam]

Updated	 via  https://github.com/Gnucash/gnucash/commit/8192deff (commit)
	from  https://github.com/Gnucash/gnucash/commit/6f6d2fef (commit)



commit 8192deff37e4a5063ad62a90753bcd9a60b2f716
Author: Christopher Lam <christopher.lck at gmail.com>
Date:   Tue Oct 25 00:17:30 2022 +0800

    [gnc-features.cpp] convert to cpp
    
    - don't need to create/destroy GHashTable for each feature query
    - plugs leak: g_hash_table_unref (features_used) not always called properly
    - to check 1 feature, don't need to traverse whole GHashTable



Summary of changes:
 libgnucash/engine/CMakeLists.txt                   |   3 +-
 .../engine/{gnc-features.c => gnc-features.cpp}    | 129 ++++-----------------
 libgnucash/engine/qofbook.cpp                      |  28 +++++
 libgnucash/engine/{gnc-session.h => qofbook.hpp}   |  17 ++-
 po/POTFILES.in                                     |   2 +-
 5 files changed, 67 insertions(+), 112 deletions(-)
 rename libgnucash/engine/{gnc-features.c => gnc-features.cpp} (53%)
 copy libgnucash/engine/{gnc-session.h => qofbook.hpp} (78%)