interp: don't close log file if it's stderr
interp: don't close log file if it's stderr

This fixes a problem that Dewey noted in private e-mail
where "puts stderr" logging was broken after loading an ngc file.
The combination of a change which used stderr as the interpreter's
default logging destination, and a change which caused interpreter objects
to be created and destroyed within a singla AXIS session led to this
problem.

bmwiedemann/linuxcnc-mirror,mhaberler/machinekit,mhaberler/machinekit,ikcalB/linuxcnc-mirror,strahlex/machinekit,unseenlaser/machinekit,Cid427/machinekit,araisrobo/machinekit,kinsamanka/machinekit,araisrobo/machinekit,araisrobo/machinekit,RunningLight/machinekit,bmwiedemann/linuxcnc-mirror,EqAfrica/machinekit,mhaberler/machinekit,RunningLight/machinekit,mhaberler/machinekit,ArcEye/MK-Qt5,kinsamanka/machinekit,ikcalB/linuxcnc-mirror,bobvanderlinden/machinekit,mhaberler/machinekit,strahlex/machinekit,unseenlaser/machinekit,EqAfrica/machinekit,kinsamanka/machinekit,unseenlaser/machinekit,bobvanderlinden/machinekit,ArcEye/MK-Qt5,EqAfrica/machinekit,bobvanderlinden/machinekit,EqAfrica/machinekit,RunningLight/machinekit,ikcalB/linuxcnc-mirror,RunningLight/machinekit,araisrobo/machinekit,EqAfrica/machinekit,ikcalB/linuxcnc-mirror,ArcEye/machinekit-testing,RunningLight/machinekit,ArcEye/MK-Qt5,kinsamanka/machinekit,Cid427/machinekit,strahlex/machinekit,EqAfrica/machinekit,ArcEye/MK-Qt5,unseenlaser/machinekit,ArcEye/machinekit-testing,mhaberler/machinekit,kinsamanka/machinekit,Cid427/machinekit,ArcEye/MK-Qt5,bmwiedemann/linuxcnc-mirror,araisrobo/machinekit,strahlex/machinekit,bobvanderlinden/machinekit,bmwiedemann/linuxcnc-mirror,kinsamanka/machinekit,mhaberler/machinekit,RunningLight/machinekit,RunningLight/machinekit,strahlex/machinekit,bobvanderlinden/machinekit,araisrobo/machinekit,ArcEye/MK-Qt5,mhaberler/machinekit,ArcEye/machinekit-testing,kinsamanka/machinekit,unseenlaser/machinekit,Cid427/machinekit,ArcEye/MK-Qt5,Cid427/machinekit,bobvanderlinden/machinekit,ArcEye/machinekit-testing,kinsamanka/machinekit,ikcalB/linuxcnc-mirror,araisrobo/machinekit,ArcEye/MK-Qt5,Cid427/machinekit,bobvanderlinden/machinekit,ikcalB/linuxcnc-mirror,Cid427/machinekit,unseenlaser/machinekit,unseenlaser/machinekit,ArcEye/machinekit-testing,ArcEye/machinekit-testing,bmwiedemann/linuxcnc-mirror,araisrobo/machinekit,bmwiedemann/linuxcnc-mirror,ArcEye/machinekit-testing,Cid427/machinekit,bobvanderlinden/machinekit,strahlex/machinekit,bmwiedemann/linuxcnc-mirror,araisrobo/machinekit,EqAfrica/machinekit,RunningLight/machinekit,EqAfrica/machinekit,unseenlaser/machinekit,strahlex/machinekit,ikcalB/linuxcnc-mirror,ArcEye/machinekit-testing