* cygheap.cc (cygheap_fixup_in_child): Use user_heap element in cygheap.

(init_cheap): Ditto for declaration.
* fork.cc (fork_parent): Use user_heap element in cygheap.
* heap.h (inheap): Ditto.
* heap.cc (sbrk): Ditto.
(heap_init): Ditto.  Reorganize to shrink heap chunk as required and record new
value in cygheap.
* dcrt0.cc (dll_crt0_1): More "move the cygthread init" games.
* shared.cc (open_shared): Rework memory protection to properly deal with
relocated shared segment.
(shared_info::heap_chunk_size): Rename element to 'heap_chunk'.
* shared_info.h (shared_info): Ditto for declaration.
* strace.cc (strace::hello): Report on heap chunk size from cygheap since it
may shrink.

winsup/cygwin/cygheap.h

@@ -198,18 +198,21 @@ struct cygheap_debug
 };
 #endif
 
+struct user_heap_info
+{
+  void *base;
+  void *ptr;
+  void *top;
+  unsigned chunk;
+};
+
 struct init_cygheap
 {
   _cmalloc_entry *chain;
   char *buckets[32];
-  struct /* User heap stuff. */
-    {
-      void *heapbase;
-      void *heapptr;
-      void *heaptop;
-    };
   cygheap_root root;
   cygheap_user user;
+  user_heap_info user_heap;
   mode_t umask;
   HANDLE shared_h;
   HANDLE console_h;