(child_info::cygheap_alloc_sz): New field.
* cygheap.cc (init_cheap): Reduce size of cygwin stack until minimal hit when
attempting initial allocation.
(cygheap_setup_for_child): Use alloc_sz to create secondary memory mapped
entry. Store alloc_sz in cygheap_alloc_sz.
(cygheap_fixup_in_child): Use cygheap_alloc_sz to map parent's cygheap.
* cygheap.h (_CYGHEAPSIZE_SLOP): New define.
(CYGHEAPSIZE): Use _CYGHEAPSIZE_SLOP.