Move headers from server/include to include/maxscale

- Headers now to be included as <maxscale/xyz.h>
- First step, no cleanup of headers has been made. Only moving
  from one place to another + necessary modifications.

server/core/random_jkiss.c

@@ -31,8 +31,8 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
-#include <spinlock.h>
-#include <random_jkiss.h>
+#include <maxscale/spinlock.h>
+#include <maxscale/random_jkiss.h>
 
 /* Public domain code for JKISS RNG - Comment header added */