Win32 build: Remove support for aqbanking < 5.x because 5.x has been released since 2010 by now.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23685 57a11ea4-9604-0410-9ed3-97b8803252fd
Win32 build: Update aqbanking to most recent version 5.3.0

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23686 57a11ea4-9604-0410-9ed3-97b8803252fd