gdb, gdbserver, gdbsupport: fix some namespace comment formatting

I noticed a

  // namespace selftests

comment, which doesn't follow our comment formatting convention.  I did
a find & replace to fix all the offenders.

Change-Id: Idf8fe9833caf1c3d99e15330db000e4bab4ec66c

gdb/cp-support.c

@@ -2267,7 +2267,7 @@ test_cp_remove_params ()
 #undef CHECK_INCOMPL
 }
 
-} // namespace selftests
+} /* namespace selftests */
 
 #endif /* GDB_SELF_CHECK */