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

* 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.