libcamera: Include header related to source file first

Include the header file corresponding to the source file in the very
first position. This complies with the Google C++ coding style
guideliens, and helps ensuring that the headers are self-contained.

Three bugs are already caught by this change (missing includes or
forward declarations) in device_enumerator.h, event_dispatcher_poll.h
and pipeline_handler.h. Fix them.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/include/device_enumerator.h

@@ -14,6 +14,9 @@
 
 #include <linux/media.h>
 
+struct udev;
+struct udev_monitor;
+
 namespace libcamera {
 
 class EventNotifier;

src/libcamera/include/event_dispatcher_poll.h

@@ -13,6 +13,8 @@
 #include <map>
 #include <vector>
 
+struct pollfd;
+
 namespace libcamera {
 
 class EventNotifier;

src/libcamera/include/pipeline_handler.h

@@ -10,6 +10,7 @@
 #include <list>
 #include <map>
 #include <memory>
+#include <set>
 #include <string>
 #include <vector>