Add new test demonstrating endless loop with incorrect G71 parameters

I found this issue in issue #1146. This example g-code program causes
the AXIS LinuxCNC GUI to get completely stuck while its memory use explode.
I decided to write a small test case to demonstrate the problem.
Discovered that the program cause the rs274 program to generate an
endless stream of repeated instructions, which I suspect is the cause of
the memory explosion.

tests/interp/g71-endless-loop/expected

@@ -0,0 +1,43 @@
+ N..... USE_LENGTH_UNITS(CANON_UNITS_MM)
+ N..... SET_G5X_OFFSET(1, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... SET_G92_OFFSET(0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... SET_XY_ROTATION(0.0000)
+ N..... SET_FEED_REFERENCE(CANON_XYZ)
+ N..... ON_RESET()
+ N..... COMMENT("G21 metric, G54 coordinate system 1, G18 ZX plane, G54 coordinate system")
+ N..... SELECT_PLANE(CANON_PLANE_XZ)
+ N..... USE_LENGTH_UNITS(CANON_UNITS_MM)
+ N..... COMMENT("interpreter: continuing to use same coordinate system")
+ N..... COMMENT("G49 cancel tool length offset")
+ N..... USE_TOOL_LENGTH_OFFSET(0.0000 0.0000 0.0000, 0.0000 0.0000 0.0000, 0.0000 0.0000 0.0000)
+ N..... COMMENT("G90 abs dist mode, G92.1 Reset coord sys offset")
+ N..... SET_G92_OFFSET(0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... COMMENT("G94 Feed Mode=Units per Minute, G64p Best Possible Speed p=Motion Blend Tolerance")
+ N..... COMMENT("interpreter: feed mode set to units per minute")
+ N..... SET_FEED_MODE(0, 0)
+ N..... SET_FEED_RATE(0.0000)
+ N..... SET_MOTION_CONTROL_MODE(CANON_CONTINUOUS, 0.001000)
+ N..... SET_NAIVECAM_TOLERANCE(0.0010)
+ N..... COMMENT("Diameter Mode = 7, Radius Mode = 8")
+ N..... COMMENT("G91.1 = Relative Arc Offset Distance")
+ N..... SET_FEED_RATE(225.0000)
+ N..... STRAIGHT_TRAVERSE(15.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_TRAVERSE(15.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(15.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(10.0400, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(10.0400, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(10.0400, 0.0000, -14.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(10.0400, 0.0000, -14.0000, 0.0000, 0.0000, 0.0000)
+ N..... ARC_FEED(-14.0400, 10.0000, -14.0000, 10.0000, 1, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(10.0000, 0.0000, -14.0400, 0.0000, 0.0000, 0.0000)
+ N..... STRAIGHT_FEED(3.0647, 0.0000, -14.0400, 0.0000, 0.0000, 0.0000)
+ N..... SET_G5X_OFFSET(1, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000)
+ N..... SET_XY_ROTATION(0.0000)
+ N..... SELECT_PLANE(CANON_PLANE_XY)
+ N..... SET_FEED_MODE(0, 0)
+ N..... SET_FEED_RATE(0.0000)
+ N..... STOP_SPINDLE_TURNING(0)
+ N..... SET_SPINDLE_MODE(0 0.0000)
+ N..... PROGRAM_END()
+ N..... ON_RESET()
+ N..... ON_RESET()

tests/interp/g71-endless-loop/g71-endless-loop.ngc

@@ -0,0 +1,19 @@
+G21 G18 G54 (G21 metric, G54 coordinate system 1, G18 ZX plane, G54 coordinate system)
+G49 (G49 cancel tool length offset)
+G90 G92.1 (G90 abs dist mode, G92.1 Reset coord sys offset)
+G94 G64 p0.001 (G94 Feed Mode=Units per Minute, G64p Best Possible Speed p=Motion Blend Tolerance)
+G8 (Diameter Mode = 7, Radius Mode = 8)
+G91.1 (G91.1 = Relative Arc Offset Distance)
+
+O200 SUB
+;Change the next line from G01 X10 Z0 to G01 X5 Z0 and Axis works fine but this isn't the part profile I need.
+G01 X10 Z0
+G01 X10 Z-14
+G01 X3
+G01 X7 Z-22
+O200 ENDSUB
+
+F225
+;G71.1 Q200 X15.0 Z0 D0.04 I0.5 R1
+G71.2 Q200 X15.0 Z0 D0.04 I0.5 R1
+M2

tests/interp/g71-endless-loop/test.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+#
+# Demonstrate endless loop when encountering incorrect parameters in
+# G71 call.  Note, the expected output is not verified.  No idea what
+# it should look like on a successful termination of this endless
+# loop.
+
+rs274 -g g71-endless-loop.ngc | awk '{$1=""; print}' > result &
+pid=$!
+
+# Give it 10 seconds to complete
+count=10
+while [ 0 -lt $count ] && kill -0 $pid > /dev/null 2>&1 ; do
+    sleep 1
+    count=$(($count - 1))
+done
+
+if kill -0 $pid > /dev/null 2>&1; then
+    kill -9 $pid
+    echo "error: g71-endless-loop.ngc program seem to be stuck, killing"
+    exit 1
+fi
+
+exit 0