current process.
(round_to_next): Obsolete function removed.
(preload_heap_section): New variable.
(data_region_size): Obsolete variable removed.
(allocate_heap): Modified to determine end of static heap section
used during preload, and use that as initial base address for
dynamic heap instead of hard-coded value.
(sbrk): Remove call to allocate_heap; handled by init_heap. Skip
calls to commit or decommit pages when allocating from static heap
section during preload.
(recreate_heap): Obsolete function removed.
(init_heap): New function to initialize internal sbrk heap
variables. Uses static heap section during preload, otherwise
calls allocate_heap to reserve a heap region dynamically.
(round_heap): Use ROUND_UP macro instead of round_to_next.
(cache_system_info): Set os_subtype.
(recreate_heap): Update system information after loading heap.
Don't use data_seg pragma here.
(_heap_init, _heap_term) [_MSC_VER >= 1000]: New functions that
override CRT routines.
into Windows 95, Windows NT, and W32, respectively.
Expand "win" substring in variables referring to Microsoft Windows
constructs into "windows".
Canonicalize header comments to use same terminology.
(allocate_heap): Use VALBITS to determine size of heap.
(allocate_heap) [WINDOWS95]: Conditional code removed.
(sbrk): Use VALMASK instead of an unsigned integer mask.
