Update to 1.3.7d
    
    - New upstream release 1.3.7d
      - Fix crash with long lines in AuthGroupFile due to large realloc(3) (GH#1321)
      - NLST did not behave consistently for relative paths (GH#1325)
      - Implement AllowForeignAddress class matching for passive data transfers
        (GH#1346)
      - DeleteAbortedStores removed successfully transferred files unexpectedly
        (Bug #4467)
      - Keepalive socket options should be set using IPPROTO_TCP, not SOL_SOCKET
        (GH#1401)
      - TCP keepalive SocketOptions should apply to control as well as data
        connection (GH#1402)
      - ProFTPD always used the same PassivePorts port for first transfer (GH#1396)
      - Name-based virtual hosts not working as expected after upgrade from 1.3.7a
        to 1.3.7b (GH#1369)
    - Use %license unconditionally