Fix declaration of ConcurrentHashMap instance

This should prevent issues with running 1.8-compiled classes on 1.6 or 1.7.
Merge pull request #1277 from sbesson/native-lib-loader_pom

Update to native-lib-loader version 2.0.2
merge dev_5_0 -Dorg -Ssuccess-only: PR 1275 (Performance and position count fixes for ND2)
merge dev_5_0 -Dorg -Ssuccess-only: PR 1280 (Fix declaration of ConcurrentHashMap instance)
merge dev_5_0 -Dorg -Ssuccess-only

Repository: openmicroscopy/bioformats
Excluded PRs:
  # PR 1282 melissalinkert 'Update version numbers to 5.0.4' (label: exclude)
  # PR 1281 melissalinkert 'Update release notes for 5.0.4' (status: error)
Updating 4a28d34..798e32e
Previously merged:
  # PR 1277 sbesson 'Update to native-lib-loader version 2.0.2'

Merged PRs:
  # PR 1275 melissalinkert 'Performance and position count fixes for ND2'
  # PR 1280 melissalinkert 'Fix declaration of ConcurrentHashMap instance'

Generated by OME-5.0-merge-push#191 (http://ci.openmicroscopy.org/job/OME-5.0-merge-push/191/)