Throughout, change fhandler_*::read and fhandler_*::raw_read to void functions

whose second arguments are both the lenght and the return value.
* fhandler.cc (fhandler_base::read): Rework slightly to use second argument as
input/output.  Tweak CRLF stuff.
(fhandler_base::readv): Accommodate fhandler_*::read changes.
* cygthread.h (cygthread::detach): Declare as taking optional handle argument.
(cygthread::detach): When given a handle argument, wait for the handle to be
signalled before waiting for thread to detach.  Return true when signal
detected.

winsup/cygwin/fhandler_serial.cc

@@ -38,8 +38,8 @@ fhandler_serial::overlapped_setup ()
   overlapped_armed = 0;
 }
 
-int
-fhandler_serial::raw_read (void *ptr, size_t ulen)
+void
+fhandler_serial::raw_read (void *ptr, size_t& ulen)
 {
   int tot;
   DWORD n;
@@ -146,7 +146,7 @@ fhandler_serial::raw_read (void *ptr, size_t ulen)
     }
 
 out:
-  return tot;
+  ulen = tot;
 }
 
 /* Cover function to WriteFile to provide Posix interface and semantics