Make header files more self-contained - add missing Ardour and lib includes

libs/pbd/pbd/atomic_counter.h

@@ -20,6 +20,8 @@
 #ifndef PBD_ATOMIC_COUNTER_H
 #define PBD_ATOMIC_COUNTER_H
 
+#include "pbd/atomic.h"
+
 #include <atomic>
 
 #include <glib.h>

libs/pbd/pbd/property_basics_impl.h

@@ -18,6 +18,8 @@
 
 #pragma once
 
+#include "pbd/property_basics.h"
+
 namespace PBD {
 
 template<typename T>

libs/pbd/pbd/scoped_file_descriptor.h

@@ -18,6 +18,8 @@
 
 #pragma once
 
+#include <unistd.h>
+
 namespace PBD {
 
 struct ScopedFileDescriptor {