Log Message:
databases/postgresql-postgis2: Remove buildlink3.mk

Postgis having a bl3 file is:

  - unused: no package (even in wip) includes it

  - conceptually wrong: When a package has postgis support, it does so
    by linking the postgresql client libs, and then sending queries
    with spatial objects across that connection.  There is nothing to
    link against.  And, just like any other use of a database, the
    server might be on some other machine -- so depending programs are
    simply clients anyway.

In theory this will change nothing and break nothing...