Add regression test for bodyless function return

The function_return output should have the correct identifier.

Author: peterschrammel

regression/cbmc/function-return-no-body1/main.c

@@ -0,0 +1,9 @@
+#include <assert.h>
+
+void no_body();
+
+void main()
+{
+  no_body();
+  assert(0);
+}

regression/cbmc/function-return-no-body1/test.desc

@@ -0,0 +1,11 @@
+CORE
+main.c
+--xml-ui
+activate-multi-line-match
+EXIT=10
+SIGNAL=0
+VERIFICATION FAILED
+<function_call hidden="false" step_nr="18" thread="0">\n\s*<function display_name="no_body" identifier="no_body">
+<function_return hidden="false" step_nr="19" thread="0">\n\s*<function display_name="no_body" identifier="no_body">
+--
+^warning: ignoring