* mmap.cc: Restructure. Add, remove and rewrite comments throughout

	* mmap.cc: Restructure. Add, remove and rewrite comments throughout
	for better readability.  Change function names for better
	understanding.
	(MAP_SET): Accomodate name change from map_map_ to page_map_.
	(MAP_CLR): Ditto.
	(MAP_ISSET): Ditto.
	(mmap_record::page_map_): Rename from page_map_.
	(mmap_record::get_map): Remove.
	(mmap_record::alloc_page_map): Rename from alloc_map. Return bool
	indicating success of cygheap memory allocation.
	(mmap_record::free_page_map): Rename from free_map.
	(mmap_record::fixup_page_map): Rename from fixup_map.
	(mmap_record::find_unused_pages): Rename from find_empty.
	(mmap_record::map_pages): Rename from map_map.
	(mmap_record::unmap_pages): Rename from unmap_map.
	(class list): Make all class members private.
	(list::list): Remove.
	(list::~list): Remove.
	(list::get_fd): New attribute reader.
	(list::get_hash): Ditto.
	(list::get_record): Ditto.
	(list::add_record): Manage all allocation for mmap_records.  Check
	for failed memory allocation and return NULL if so.
	(list::set): New function.
	(list::del_record): Rename from erase. Return true if last mmap_record
	has been deleted, false otherwise. Check for legal incoming index
	value.
	(list::erase): Remove erase/0.
	(list::search_record): Rename from match.
	(map::map): Remove.
	(map::~map): Remove.
	(map::add_list): Manage all allocation for lists.  Check for failed
	memory allocation and return NULL if so.
	(map::get_list): New method.
	(map::del_list): Rename from erase. Check for legal incoming index
	value.
	(mmap64): Check for failed mmap_record memory allocation.  Return
	with MAP_FAILED and errno set to ENOMEM if so.
	(munmap): Rearrange loop using new list and mmap_record accessor
	functions.  Rename loop index variables for better understanding.
	Check if list can be deleted after last mmap_record in it has been
	deleted.
	(msync): Rearrange loop using new list and mmap_record accessor
	functions.  Rename loop index variables for better understanding.
	(fixup_mmaps_after_fork): Ditto.