* dwarf2read.c: Don't include zlib.h or sys/mman.h.

	* dwarf2read.c: Don't include zlib.h or sys/mman.h.
	(pagesize): Remove.
	(struct dwarf2_section_info) <map_addr, map_len>: Remove.
	(zlib_decompress_section): Remove.
	(dwarf2_read_section): Use gdb_bfd_map_section.
	(munmap_section_buffer): Remove.
	(free_dwo_file, dwarf2_per_objfile_free): Don't use
	munmap_section_buffer.
	* gdb_bfd.c: Include zlib.h, sys/mman.h.
	(struct gdb_bfd_section_data): New.
	(free_one_bfd_section): New function.
	(gdb_bfd_close_or_warn): Use free_one_bfd_section.
	(get_section_descriptor, zlib_decompress_section)
	(gdb_bfd_map_section): New functions.
	* gdb_bfd.h (gdb_bfd_map_section): Declare.