no visible binding for global variable

[ssnn]

Fix this win-builder message:

* checking R code for possible problems ... [62s] NOTE
getCloneRegion: no visible binding for global variable
  'IMGT_VDJ_BY_REGIONS'
makeRegion: no visible binding for global variable
  'IMGT_VDJ_BY_REGIONS'
makeRegion: no visible binding for global variable 'IMGT_V_BY_REGIONS'
Undefined global functions or variables:
  IMGT_VDJ_BY_REGIONS IMGT_V_BY_REGIONS

‌

[ssnn]

39b21a6