add (very simple) example for dbg.h

samples/debug.c

@@ -0,0 +1,12 @@
+
+#include <dbg.h>
+
+int main(void)
+{
+    /* DbgInit has to be called once, to install the BRK handler */
+    DbgInit(0);
+
+    /* now to break into the debugger, use the BREAK macro */
+    BREAK();
+    return 0;
+}