* cygheap.h (init_cygheap): New struct holding values that live in the Cygwin

* cygheap.h (init_cygheap): New struct holding values that live in the Cygwin
heap.
* child_info.h (child_info): Change pointer type of cygheap to init_cygheap.
* cygheap.cc (init_cheap): Point cygheap_max after contents of cygheap.  Move
some stuff into cygheap.h.
* dir.cc (opendir): Change to use root and rootlen in cygheap rather than in
myself.
(mkdir): Change to use umask in cygheap rather than in myself.
* path.cc: Ditto, throughout.
* syscalls.cc (_open): Ditto.  Change to use umask in cygheap rather than in
myself.
(chroot): Change to allocate root dir on the cygwin heap.
(umask): Change to use umask in cygheap rather than in myself.
(cygwin_bind): Ditto.
* sigproc.cc (proc_subproc): Don't copy umask or root stuff as this happens
automatically now.
* pinfo.h (_pinfo): Migrate stuff out of here and into init_cheap.
* dcrt0.cc (dll_crt0_1): Call cygheap_init later in startup for first cygwin
process.