hdfview

Merge pull request #260 in HDFVIEW/hdfview from ~BYRN/hdfview_adb:master to master

* commit '3c6d1b2140568a0ad28adaf3e8c28412e2e2567c':
  Correct second hdf5 target name to hdf4
  HDFVIEW-245/235 make hdf4 optional