core: normalize header inclusion in execute.h a bit

We don't actually need any functionality from cgroup.h in execute.h, hence
don't include that. However, we do need the Unit structure from unit.h, hence
include that, and move it as late as possible, since it needs the definitions
from execute.h.

src/core/execute.h

@@ -30,6 +30,7 @@ typedef struct ExecParameters ExecParameters;
 #include <stdio.h>
 #include <sys/capability.h>
 
+#include "cgroup-util.h"
 #include "fdset.h"
 #include "list.h"
 #include "missing.h"
@@ -203,9 +204,6 @@ struct ExecContext {
         bool no_new_privileges_set:1;
 };
 
-#include "cgroup-util.h"
-#include "cgroup.h"
-
 struct ExecParameters {
         char **argv;
         char **environment;
@@ -236,6 +234,8 @@ struct ExecParameters {
         int stderr_fd;
 };
 
+#include "unit.h"
+
 int exec_spawn(Unit *unit,
                ExecCommand *command,
                const ExecContext *context,

src/core/scope.h

@@ -21,7 +21,9 @@
 
 typedef struct Scope Scope;
 
+#include "cgroup.h"
 #include "kill.h"
+#include "unit.h"
 
 typedef enum ScopeResult {
         SCOPE_SUCCESS,