for the purpose of comparing different compression algorithms.

PAGE_ZIP_COMPRESS_DBG: New preprocessor condition, to see if deflate()
is wrapped.

page_zip_compress_log: Log file counter.  If set to nonzero, logging
is enabled.

page_zip_compress_deflate(): Add the parameter logfile.

FILE_LOGFILE, LOGFILE: Macros for declaring and passing the parameter logfile.

page_zip_compress(): Open and close the logfile if needed.  Write the
uncompressed page and the size of the compressed data.  The data passed
to deflate() is written by the wrapper page_zip_compress_deflate().