Include string.h (not strings.h) to avoid warning about implicit declaration of strcmp

src/rds_wav.c

@@ -26,7 +26,7 @@
 #include <stdlib.h>
 #include <math.h>
 #include <sndfile.h>
-#include <strings.h>
+#include <string.h>
 
 #include "rds.h"
 #include "fm_mpx.h"
@@ -98,4 +98,4 @@ int main(int argc, char **argv) {
     fm_mpx_close();
 
     return EXIT_SUCCESS;
-}
+}