the import() module's file parameter doesn't accept absolute path
WARNING: Can't open DXF file '/tmp/tmp/plan.dxf'.
it seems paths are just concatenated to $PWD instead of being
interpreted like usual.
while looking around for where to fix this, i found that the library
path configuration in parsersettings.cc is rather unflexible; what would
you think about accepting a OPENSCADPATH environment variable in the
same spirit as python's PYTHONPATH or a shell's PATH? this would allow
users to use their own libraries without either having to specify
absolute paths or having to requiring write permissions on /usr/share/.
Added test cases for issue #123
Don't prefix filenames which are already absolute with document path.…
… Fixed #123