Parker weighting issues no warning with large source offsets

[SimonRit]

See the conversation on the mailing list.

This code

rtksimulatedgeometry -v -o geometry_sx_220_600.xml -a 220 -f -110 -n 300 --sid 1172.2 --sdd 1672.2 --proj_iso_x 60 --source_x 60
rtkprojectshepploganphantom -g geometry_sx_220_600.xml -o proj1.mha --dimension 512,3
rtkfdk --dimension 256,1,256 -p . -r proj1.mha -o fdk1.mha -g geometry_sx_220_600.xml --nodisplaced

produces a bad result, most likely due to insufficient data. But RTK does not issue a warning.
This acquisition produces a correct result, showing that Parker seems to account correctly for source offsets:

rtksimulatedgeometry -v -o geometry_sx_220_600.xml -a 220 -f -110 -n 300 --sid 1172.2 --sdd 1672.2 --proj_iso_x -60 --source_x -60
rtkprojectshepploganphantom -g geometry_sx_220_600.xml -o proj1.mha --dimension 512,3
rtkfdk --dimension 256,1,256 -p . -r proj1.mha -o fdk1.mha -g geometry_sx_220_600.xml --nodisplaced