adds tests/metrics

tests/metrics/func_ptr.c

 /* run.config
-   STDOPT: +"-metrics-eva-cover -metrics-cover main -load-module scope"
-   STDOPT: +"-metrics-eva-cover -main foobar -metrics-cover foobar -load-module scope"
+   STDOPT: +"-metrics-eva-cover -metrics-cover main"
+   STDOPT: +"-metrics-eva-cover -main foobar -metrics-cover foobar"
 **/
 
 void (*bar) (int);  extern void (*bar_extern) (int);

tests/metrics/reach.c

 /* run.config
-   STDOPT: +"-metrics-by-function -metrics-eva-cover -load-module scope"
+   STDOPT: +"-metrics-by-function -metrics-eva-cover"
 **/
 
 void (*bar) (int); void (*t[2])(int);

tests/metrics/test_config

 PLUGIN: metrics
-OPT: -load-module scope -metrics
+OPT: -metrics

tests/metrics/unreachable.c

 /* run.config
-   STDOPT: +"-load-module scope -metrics-eva-cover -then -main foo"
+   STDOPT: +"-metrics-eva-cover -then -main foo"
 **/
 void foo () {
   int i = 0;