Lack of namespace causes issues with external build tools

[catmxt]

We are compiling the library as part of an Unreal Engine project, which means ignoring the CMakeLists.txt. We have found that in certain situations, name collisions happen between elements in odrSpiral.cpp and the included dependency pugixml.cpp, causing a compilation failure.

...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(4409): error C4459: declaration of 'sn' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(48): note: see declaration of 'sn'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(4426): error C4459: declaration of 'sn' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(48): note: see declaration of 'sn'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(12606): error C4459: declaration of 'sd' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(56): note: see declaration of 'sd'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(12627): error C4459: declaration of 'sd' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(56): note: see declaration of 'sd'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(12649): error C4459: declaration of 'sd' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(56): note: see declaration of 'sd'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(12669): error C4459: declaration of 'sd' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(56): note: see declaration of 'sd'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(12702): error C4459: declaration of 'sd' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(56): note: see declaration of 'sd'
...\libOpenDRIVE\thirdparty\pugixml\pugixml.cpp(12724): error C4459: declaration of 'sd' hides global declaration
...\libOpenDRIVE\src\Geometries\Spiral\odrSpiral.cpp(56): note: see declaration of 'sd'

Adding code in odrSpiral.h and odrSpiral.cpp to the odr namespace resolves the issue.

[pageldev]

makes sense, thx!