lang/gnatdroid-armv(5,7): Convert to staging
* PORTREVISION bumped because previous package added empty directories.
* GPLv3 LICENSE added, but not installed as it messed up dynamic PLIST
* pkg-message used instead of post-install echoes
* Custom do-build target removed, default works after modifications
* OPTIONS_SUB=yes to handle standard PLIST_SUB conversions
* Auto-PLIST logic improvements
* To simplify Auto-PLIST, non-bin entries were removed from pkg-plist
* It was necessary to add pre-install target to pre-create directories that
are no longer present when port is installed in clean stage.