Style: Harmonize header includes in platform ports

This applies our existing style guide, and adds a new rule to that style
guide for modular components such as platform ports and modules:

Includes from the platform port or module should be included with relative
paths (relative to the root folder of the modular component, e.g.
`platform/linuxbsd/`), in their own section before Godot's "core" includes.

The `api` and `export` subfolders also need to be handled as self-contained
(and thus use relative paths for their "local" includes) as they are all
compiled for each editor platform, without necessarily having the api/export
matching platform folder in the include path.
E.g. the Linux editor build will compile `platform/android/{api,export}/*.cpp`
and those need to use relative includes for it to work.

platform/linuxbsd/x11/detect_prime_x11.cpp

@@ -28,29 +28,26 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
 /**************************************************************************/
 
-#ifdef X11_ENABLED
-#if defined(GLES3_ENABLED)
+#if defined(X11_ENABLED) && defined(GLES3_ENABLED)
 
 #include "detect_prime_x11.h"
 
 #include "core/string/print_string.h"
 #include "core/string/ustring.h"
 
-#include <stdlib.h>
-
 #include "thirdparty/glad/glad/gl.h"
 #include "thirdparty/glad/glad/glx.h"
 
 #ifdef SOWRAP_ENABLED
-#include "dynwrappers/xlib-so_wrap.h"
+#include "x11/dynwrappers/xlib-so_wrap.h"
 #else
 #include <X11/XKBlib.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #endif
 
-#include <cstring>
-
+#include <stdlib.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -265,5 +262,4 @@ int detect_prime() {
 	return preferred;
 }
 
-#endif
-#endif
+#endif // X11_ENABLED && GLES3_ENABLED