message: Fix forkAtNextBlock comments
  sync the comments with what the helper function actually test, i.e. MTP
  >= fork time rather than >.
  While at it fix a typo in the comment and imporve the format of comments
  ued to descirbe the general aim of this set of helper.
diff: @@ -136,10 +136,11 @@ void CBlockIndex::BuildSkip()
  * on e.g. block size in the UAHF case.
  *
  * The following helper will check if a given block belongs to 4 different intervals, namely:
  - * - [x,+inf)
  - * - [x,x]
  - * - [x-1,+inf)
  - * - [x-1,x-1]
  + *
  + * - forkActivated: [x,+inf)
  + * - forkActivateNow: [x,x]
  + * - forkActiveOnNextBlock: [x-1,+inf)
  + * - forkAtNextBlock: [x-1,x-1]
  */
  /** return true for every block from fork block and forward [x,+inf)
  @@ -180,9 +181,9 @@ bool CBlockIndex::IsforkActiveOnNextBlock(int time) const
  return false;
  }
  -/* return true only if 1st condition is true (Median past time > UAHF time)
  +/* return true only if 1st condition is true (Median past time >= fork time)
  * and not the 2nd, i.e. we are at precisely [x-1,x-1]
  - * state: fork enabled but not activateda */
  + * state: fork enabled but not activated */
  bool CBlockIndex::forkAtNextBlock(int time) const
  {
  if (time == 0)
  