OSR proj.4 import: for HOM, make sure +no_off/no_uoff is preserved, and change default value of gamma parameter to be the same as alpha (#5511)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27436 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_mingw_w64