spa: libcamera: compile fully as C++

There was one file "libcamera.c" that was a C source file, which
prevents the addition of C++ functions, includes, etc. to "libcamera.h".
So compile that file as C++ as well.

spa/plugins/libcamera/libcamera-device.cpp

@@ -21,7 +21,7 @@
 #include <spa/monitor/utils.h>
 #include <spa/param/param.h>
 
-#include "libcamera.h"
+#include "libcamera.hpp"
 #include "libcamera-manager.hpp"
 
 #include <libcamera/camera.h>

spa/plugins/libcamera/libcamera-manager.cpp

@@ -25,7 +25,7 @@ using namespace libcamera;
 #include <spa/monitor/device.h>
 #include <spa/monitor/utils.h>
 
-#include "libcamera.h"
+#include "libcamera.hpp"
 #include "libcamera-manager.hpp"
 
 namespace {

spa/plugins/libcamera/libcamera-source.cpp

@@ -42,7 +42,7 @@
 #include <libcamera/framebuffer.h>
 #include <libcamera/framebuffer_allocator.h>
 
-#include "libcamera.h"
+#include "libcamera.hpp"
 #include "libcamera-manager.hpp"
 
 using namespace libcamera;

spa/plugins/libcamera/libcamera.cpp

@@ -5,7 +5,9 @@
 #include <spa/support/plugin.h>
 #include <spa/support/log.h>
 
-#include "libcamera.h"
+#include "libcamera.hpp"
+
+extern "C" {
 
 SPA_LOG_TOPIC_DEFINE(libcamera_log_topic, "spa.libcamera");
 
@@ -34,3 +36,5 @@ int spa_handle_factory_enum(const struct spa_handle_factory **factory,
 	(*index)++;
 	return 1;
 }
+
+}

spa/plugins/libcamera/libcamera.hpp

@@ -6,9 +6,7 @@
 
 #include <spa/support/log.h>
 
-#ifdef __cplusplus
 extern "C" {
-#endif /* __cplusplus */
 
 extern const struct spa_handle_factory spa_libcamera_source_factory;
 extern const struct spa_handle_factory spa_libcamera_manager_factory;
@@ -18,11 +16,9 @@ extern const struct spa_handle_factory spa_libcamera_device_factory;
 #define SPA_LOG_TOPIC_DEFAULT &libcamera_log_topic
 extern struct spa_log_topic libcamera_log_topic;
 
+}
+
 static inline void libcamera_log_topic_init(struct spa_log *log)
 {
 	spa_log_topic_init(log, &libcamera_log_topic);
 }
-
-#ifdef __cplusplus
-}
-#endif /* __cplusplus */

spa/plugins/libcamera/meson.build

@@ -1,5 +1,5 @@
 libcamera_sources = [
-  'libcamera.c',
+  'libcamera.cpp',
   'libcamera-manager.cpp',
   'libcamera-device.cpp',
   'libcamera-source.cpp'