[gradsusr] [Bug report] gxout shape in -poly mode does not honor clevs or cint

[Stefan Gofferje]

Grads version: 2.2.1
Platform: Ubuntu Server 16.04

Observed behaviour:
When using gxout shp with shpopts -poly to create shapefiles, grads does 
not honor clevs or cint setting issued before the draw command.
With shpopts -line, cint and/or clevs ARE honored

Expected behaviour:
Grads should honor clevs/cint settings also when creating shape files in 
-poly mode.