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/testtool.c

@@ -43,6 +43,7 @@
 */
 #include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <setjmp.h>
 
 #include "lispemul.h"