docs: improvements to source code documentation (#1236)

src/platform/linux/misc.h

@@ -1,5 +1,4 @@
-#ifndef SUNSHINE_PLATFORM_MISC_H
-#define SUNSHINE_PLATFORM_MISC_H
+#pragma once
 
 #include <unistd.h>
 #include <vector>
@@ -29,5 +28,3 @@ namespace dyn {
   handle(const std::vector<const char *> &libs);
 
 }  // namespace dyn
-
-#endif