interp_convert.c:fix logic detecting rotaryindexer
interp_convert.c:fix logic detecting rotaryindexer

detected by runtests

formerly: a_indexer      was boolean
now     : a_indexer_jnum is the number of the joint
                         (-1 ==> not in use)

Signed-off-by: Dewey Garrett <546ec366615570e68497e3c5df9092106a9808f4@panix.com>

ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror