[tests] update test for #840 and set oracle

tests/slicing/function_lvar.i

 /* run.config*
-OPT: -slice-pragma main
+OPT: -slice-pragma main -then-last -print
 */
 int g(int x) { return x; }
 

tests/slicing/oracle/function_lvar.res.oracle

+[kernel] Parsing tests/slicing/function_lvar.i (no preprocessing)
+[slicing] slicing requests in progress...
+[eva] Analyzing a complete application starting at main
+[eva] Computing initial state
+[eva] Initial state computed
+[eva:initial-state] Values of globals at initialization
+  
+[eva] done for function main
+[eva:summary] ====== ANALYSIS SUMMARY ======
+  ----------------------------------------------------------------------------
+  2 functions analyzed (out of 2): 100% coverage.
+  In these functions, 5 statements reached (out of 5): 100% coverage.
+  ----------------------------------------------------------------------------
+  No errors or warnings raised during the analysis.
+  ----------------------------------------------------------------------------
+  0 alarms generated by the analysis.
+  ----------------------------------------------------------------------------
+  Evaluation of the logical properties reached by the analysis:
+    Assertions        1 valid     0 unknown     0 invalid      1 total
+    Preconditions     0 valid     0 unknown     0 invalid      0 total
+  100% of the logical properties reached have been proven.
+  ----------------------------------------------------------------------------
+[slicing] initializing slicing ...
+[slicing] interpreting slicing requests from the command line...
+[pdg] computing for function main
+[from] Computing for function g
+[from] Done for function g
+[pdg] done for function main
+[slicing] applying all slicing requests...
+[slicing] applying 0 actions...
+[slicing] applying all slicing requests...
+[slicing] applying 1 actions...
+[slicing] applying actions: 1/1...
+[pdg] computing for function g
+[pdg] done for function g
+[slicing] exporting project to 'Slicing export'...
+[slicing] applying all slicing requests...
+[slicing] applying 0 actions...
+[sparecode] remove unused global declarations from project 'Slicing export tmp'
+[sparecode] removed unused global declarations in new project 'Slicing export'
+/* Generated by Frama-C */
+int g(int x);
+
+void g_slice_1(void)
+{
+  return;
+}
+
+void main(void)
+{
+  /*@ assert &g ≡ &g; */ ;
+  /*@ slice pragma stmt; */
+  g_slice_1();
+  return;
+}
+
+