rewrite comments into one, unified style

code/user/personalities/posix/posix_fd.h

@@ -1,5 +1,7 @@
+// POSIX compatibility support for posix fd.
+
 #pragma once
-// posix_fd.h - file descriptor table (internal to posix.dll)
+// posix_fd.h - file descriptor table (internal to posix.dll).
 #include <stdint.h>
 #include <stdbool.h>