Add test for dead code messages (issue #94)

Automatic testing wasn't possible in #785 (comment),
but is now with cram.

tests/regression/issue-94.t/issue-94.c

@@ -0,0 +1,14 @@
+#include <assert.h>
+
+int main() {
+  int x;
+  if (1)
+    x = 1;
+  else
+    x = 2;
+  if (x)
+    x = 1;
+  else
+    x = 2;
+  assert(x > 1 && x < 0);
+}

tests/regression/issue-94.t/run.t

@@ -0,0 +1,13 @@
+  $ goblint --enable ana.dead-code.lines --enable ana.dead-code.branches issue-94.c
+  [Error][Assert] Assertion "tmp" will fail. (issue-94.c:13:3-13:35)
+  [Warning][Deadcode] Function 'main' has dead code:
+    on line 8 (issue-94.c:8-8)
+    on line 12 (issue-94.c:12-12)
+    on line 14 (issue-94.c:14-14)
+  [Warning][Deadcode] Logical lines of code (LLoC) summary:
+    live: 6
+    dead: 3
+    total: 9
+  [Warning][Deadcode][CWE-571] condition '1' is always true (issue-94.c:5:7-5:8)
+  [Warning][Deadcode][CWE-571] condition 'x' is always true (issue-94.c:9:7-9:8)
+  [Warning][Deadcode][CWE-570] condition 'x > 1' (possibly inserted by CIL) is always false (issue-94.c:13:3-13:35)