message: explain disable-checkpoints configure flag
diff: @@ -244,11 +244,18 @@ disable-wallet mode with:
  ./configure --disable-wallet
  -In this case there is no dependency on Berkeley DB 4.8.
  +In this case there is no dependency on Berkeley DB.
  Mining is also possible in disable-wallet mode, but only using the `getblocktemplate` RPC
  call not `getwork`.
  +Disable checkpoints
  +-------------------
  +It is possible to compile the node without the support for centrally issued checkpoints:
  +
  + ./configure --disable-checkpoints
  +
  +
  Additional Configure Flags
  --------------------------
  A list of additional configure flags can be displayed with:
  