* mmap.cc (class mmap_record): Declare new map_pages method with

	* mmap.cc (class mmap_record): Declare new map_pages method with
	address parameter.
	(mmap_record::map_pages): New method with address parameter.
	(mmap64): Evaluate access mode before checking if already existing
	mapping can be used.
	Only use existing mapping if requested access mode matches the one
	in the existing mapping.
	Add check for existing mapping for MAP_FIXED case.