cygcheck wihtout package checking if they are unavailable.
* dump_setup.cc: Generate dummy zlib macros when zlib is not available.
(open_package_list): Use zlib functions to uncompress package lists. Return
gzFile rather than FILE *.
(check_package_files): Change fp to gzFile to accommodate zlib functions. Use
gzgets to read from package file. Use gzclose to close the handle.
(package_list): Ditto.
(package_find): Ditto.