setup_native/source/win32/customactions/shellextensions in MSI Installer compiled as UNICODE

Functions suffixed with A/W (ANSI/Wide) as needed for clarity

Change-Id: I711f781b47c0efdb1e3d9bf995f7658dbb0e38d1
Reviewed-on: https://gerrit.libreoffice.org/25556Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>