Guile examples consistency changes

Use new guile_embedded_run target or guile_run target for running the
examples like the other target languages (for suppressing stdout if run
from top level).

Consistency with other target language file renames: use runme.scm for
scripts and example.i, example.c for example code.

Add class example to examples being tested.

Examples/guile/port/example.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <errno.h>
+
+void print_int(FILE *f, int i)
+{
+  if (fprintf(f, "%d\n", i)<0)
+    perror("print_int");
+}
+
+int read_int(FILE *f)
+{
+  int i;
+  if (fscanf(f, "%d", &i)!=1) {
+    fprintf(stderr, "read_int: error reading from file\n");
+    perror("read_int");
+  }
+  return i;
+}