cat/oce: Update 0.18.3.

- Fix some typos / some rephrasing in README
- Update for vtk 8
- Fixed osx issue with xlocale
- Added missing Precision.hxx header
- Added missing header in Quantity_Color_1.hxx
- Fixed MinGW issue in OSD_MemInfo.cxx
- travis-ci (gcc-5/6/7, osx images) and appveyor updates (Mingw)

(fhajny)