all: include-what-you-see fixes

After uint32_t fix from 1e82461875
it was good idea to check which headers where needed where. And
generally clean up the includes while doing the check.

src/sort.c

@@ -34,8 +34,10 @@
  */
 
 #include <config.h>
+
 #include <err.h>
 #include <errno.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>