Fix "since" entries in BPropertyInfo.

These methods and fields are missing from the R4 and R5 Be Book, but are
mentionned in the R4 release notes and present in the R5 headers.

Change-Id: I4de8298449bd66e0ee7fe0b52690552916314123
Reviewed-on: https://review.haiku-os.org/820
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

Add BPropertyInfo class docs