* spawn.cc (av::dup_maybe): Make function void rather than void *.

* environ.cc (environ_init): Remember to reparse CYGWIN if envp is
supplied.
* heap.cc (_sbrk): Remember frame for signal handling.
* syscalls.cc (read_handler): Eliminate.
(_read): Move read_handler code here.  Reorganize for one path through
'ready_for_read'.

winsup/cygwin/spawn.cc

@@ -273,7 +273,7 @@ public:
 	calloced = 1;
       }
   }
-  void *dup_maybe (int i)
+  void dup_maybe (int i)
   {
     if (i >= calloced)
       argv[i] = cstrdup (argv[i]);