Add tests verifying the incremental status is output

Author: Thomas Kiley

regression/cbmc-incr-oneloop/alarm2/test-json-output.desc

@@ -5,5 +5,6 @@ main.c
 ^SIGNAL=0$
 "messageText": "VERIFICATION FAILED"
 "currentUnwinding": 1
+"incrementalStatus": "INCONCLUSIVE"
 --
 ^warning: ignoring

regression/cbmc-incr-oneloop/alarm2/test-xml-output.desc

@@ -6,5 +6,6 @@ main.c
 <text>VERIFICATION FAILED</text>
 <current-unwinding>1</current-unwinding>
 <refinement-iteration>1</refinement-iteration>
+<incremental-status>INCONCLUSIVE</incremental-status>
 --
 ^warning: ignoring

regression/cbmc-incr-oneloop/alarm2/test.desc

@@ -1,9 +1,15 @@
 CORE
 main.c
 --incremental-loop main.0 --unwind-min 5 --unwind-max 10
+activate-multi-line-match
 Current unwinding: 1
+Incremental status: INCONCLUSIVE
+Current unwinding: 5\nUnwinding .*\nIncremental status: INCONCLUSIVE
+Current unwinding: 6\nUnwinding .*\nIncremental status: INCONCLUSIVE
 ^EXIT=10$
 ^SIGNAL=0$
 ^VERIFICATION FAILED$
 --
 ^warning: ignoring
+--
+The multi-line match is added to verify that an incremental status is printed immediately after each unwinding