Update/refactor build_multilib_wine script

• check_package_dependencies(): replace use of: command -v ; with: dpkg-query
• set_lsb_codename(), set_lsb_distribution_id(): update LSB code names (Ubuntu 20.04)
• get_optimum_repository_mirror(): revert to using netselect (Ubuntu)
• get_optimum_repository_mirror(): fix buster/bullseye LSB codename supplied to
  netselect-apt (Debian)
• fetch_wine_addon(): fix wine-gecko, wine-mono separator, arch-suffix
• add function: wine_winecfg_about_enhancement()
• add function: wine_fix_block_scope_compound_literals()
• schroot_image_bootstrap(): fix/update Schroot fstab file
• setup_chroot_build_env(), upgrade_chroot_build_env(): use:
  -o Dpkg::Options::="--force-confnew"
export DEBIAN_FRONTEND="noninteractive"
  to force non-interactive package update/installation
• src_prepare(): change patching order (apply: Wine-Staging patchset first)
• src_prepare(): update stock patches
• main(): update gentoo-wine-ebuild-common to version: 20200629