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_random.cc

@@ -110,27 +110,33 @@ fhandler_dev_random::pseudo_read (void *ptr, size_t len)
   return len;
 }
 
-int __stdcall
-fhandler_dev_random::read (void *ptr, size_t len)
+void __stdcall
+fhandler_dev_random::read (void *ptr, size_t& len)
 {
   if (!len)
-    return 0;
+    return;
+
   if (!ptr)
     {
       set_errno (EINVAL);
-      return -1;
+      (ssize_t) len = -1;
+      return;
     }
 
   if (crypt_gen_random (ptr, len))
-    return len;
+    return;
+
   /* If device is /dev/urandom, use pseudo number generator as fallback.
      Don't do this for /dev/random since it's intended for uses that need
      very high quality randomness. */
   if (unit == URANDOM)
-    return pseudo_read (ptr, len);
+    {
+      len = pseudo_read (ptr, len);
+      return;
+    }
 
   __seterrno ();
-  return -1;
+  (ssize_t) len = -1;
 }
 
 __off64_t