Reads a file, decompresses it and writes it to standard output.
Readgzfile() can be used to read a file which is not in gzip format; in this case readgzfile() will directly read from the file without decompression.
Returns the number of (uncompressed) bytes read from the file. If an error occurs, false is returned and unless the function was called as @readgzfile, an error message is printed.
The file filename will be opened from the filesystem and its contents written to standard output.
You can use the optional second parameter and set it to "1", if you want to search for the file in the include_path, too.