Files should explicitly include the definitions they directly depend on (#355)

... start by fixing the include files and the fallout in C source from
removing includes not directly needed by headers that previously included
them.

src/tstsout.c

@@ -14,6 +14,7 @@
 #include "version.h"
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
 #include <sys/file.h>