Refactor ccompile.h to not include system headers

This is a step toward being able to vendor the OpenZFS code in FreeBSD.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #10625

module/os/freebsd/spl/spl_string.c

@@ -25,6 +25,7 @@
  * Use is subject to license terms.
  */
 
+#include <sys/types.h>
 #include <sys/param.h>
 #include <sys/string.h>
 #include <sys/kmem.h>