Merge pull request #17 from stonier/win-porting

win32 porting for all of ecl_core
Merge pull request #21 from stonier/win-porting

fix missed dll exporting.
Merge pull request #22 from stonier/win-porting

fix inclusion missing in ecl_devices.
Merge branch 'win-porting' into groovy-devel
remove unused if macros for internal eigen.
message indicating internal eigen use if eigen not found.
proper header referencing utilising cmake variables for eigen.