- subdivide g:qfenter_keep_quickfixfocus option for each command.
  e.g. g:qfenter_keep_quickfixfocus.open, g:qfenter_keep_quickfixfocus.cnext,
  g:qfenter_keep_quickfixfocus.cprev
- bug fix : not updated window for already opened file when g:qfenter_keep_quickfixfocus==1
- thanks for mMontu!