driver/*.c: Add response for get_arg("mmc-supported?")

example/*.c: remove compiler wranings.

example/cdchange.c

@@ -20,6 +20,10 @@
 /* Test media changed */
 #include <stdio.h>
 
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
 #ifdef HAVE_LIMITS_H
 #include <limits.h>
 #endif
@@ -32,6 +36,10 @@
 # include <string.h>
 #endif
 
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
 #ifdef HAVE_ERRNO_H
 # include <errno.h>
 #endif