Test for if-then-else optimisation in goto convert

The optimisation has been inadvertently broken by 199d4cc
due to lack of a regression test.

Author: peterschrammel

jbmc/regression/jbmc/JumpSimplification/Test.class

@@ -0,0 +1,14 @@
+public class Test {
+
+    public int foo(int i) {
+      int x = 0;
+      if (i > 0) {
+        x++;
+      }
+      else
+      {
+        x--;
+      }
+      return x + 1000;
+    }
+}

jbmc/regression/jbmc/JumpSimplification/Test.java

@@ -0,0 +1,10 @@
+KNOWNBUG
+Test.class
+--show-goto-functions --function Test.foo
+activate-multi-line-match
+EXIT=0
+SIGNAL=0
+IF \w* <= 0 THEN GOTO 1\n\s*//.*\n\s*//.*\n\s*\w*::
+--
+IF !\(\w* <= 0\) THEN GOTO 1\n\s*//.*\n.*GOTO 2\n\s*//.*\n\s*//.*\n\s*1: \w*::
+^warning: ignoring