* ntdll.h (FILE_PIPE_*): Define constants.

* select.cc (pipe_data_available): Detect closing state.

winsup/cygwin/ntdll.h

@@ -800,6 +800,14 @@ typedef struct _FILE_ALL_INFORMATION {
   FILE_NAME_INFORMATION      NameInformation;
 } FILE_ALL_INFORMATION, *PFILE_ALL_INFORMATION;
 
+enum
+{
+  FILE_PIPE_DISCONNECTED_STATE = 1,
+  FILE_PIPE_LISTENING_STATE = 2,
+  FILE_PIPE_CONNECTED_STATE = 3,
+  FILE_PIPE_CLOSING_STATE = 4
+};
+
 typedef struct _FILE_PIPE_LOCAL_INFORMATION
 {
   ULONG NamedPipeType;