* cygheap.h (user_heap_info::sbrk): Declare new function.

(user_heap_info::init): Ditto.
* heap.cc (user_heap_info::init): Rename from heap_init().  Avoid explictly
using cygheap->user_heap.
(sbrk): Use user_heap_info method via cygheap->user_heap.
(user_heap_info::sbrk): Renamed from sbrk().  Eliminate explicit use of
cygheap->user_heap.  Change some pointer arithmetic to use (char *) for
consistency.
* shared.cc (shared_info::initialize): Change heap_init call to
cygheap->user_heap.init.

winsup/cygwin/cygheap.h

@@ -351,6 +351,8 @@ struct user_heap_info
   void *top;
   void *max;
   SIZE_T chunk;
+  void __reg2 *sbrk (ptrdiff_t);
+  void __reg1 init ();
 };
 
 struct hook_chain