Add options for some drivers
Add checks for dependences
Add cmake support for AIRSAR Polarimetric driver

This also adds a macro, add_optional_frmt_subdir() to make adding formats
cleaner.
Merge pull request #20 from simonsonc/airsar

Add cmake support for AIRSAR Polarimetric driver
Add cmake support for various drivers

This change adds support for:
* rs2: RadarSat2 XML
* ilwis: ILWIS Raster Map
* sgi: SGI Image Format
* srtmhgt: SRTM HGT Format
* leveller: Daylon Leveller Heightfield
* terragen: Terragen Heightfield
* fit: FIT
* rmf: Raster Matrix Format
* gsg: Golden Software
Merge pull request #21 from simonsonc/various

Add cmake support for various drivers
Make it easier to find HDF libraries on Ubuntu
Merge pull request #22 from simonsonc/hdf

Make it easier to find HDF libraries on Ubuntu
Add cmake support for various drivers
Merge pull request #23 from simonsonc/various

Add cmake support for various drivers
Add missing include for USGSDEM
Merge pull request #24 from simonsonc/usgsdem-fix

Add missing include for USGSDEM
Fix HDF4 driver cmake script
FixUnicode to UTF8 recodfe in sxf
Fix #5647
FixUnicode to UTF8 recodfe in sxf
Merge branch 'rsmd-reader-dev' of https://github.com/nextgis/gdal-svn into rsmd-reader-dev
Merge branch 'rsmd-reader-dev' of https://github.com/nextgis/gdal-svn into rsmd-reader-dev