Added a new test that would fail with the wrong logic in the remove_internal_symbols static condition.

Author: NlightNFotis

regression/cbmc/Static4/main.c

@@ -0,0 +1,4 @@
+static int foo(int a)
+{
+  return a+1;
+}

regression/cbmc/Static4/test.desc

@@ -0,0 +1,7 @@
+CORE
+main.c
+--show-symbol-table
+^EXIT=0$
+^SIGNAL=0$
+--
+^Symbol......: foo