/*
 * call-seq:
 *    readlines(filename, separator="\n")
 *
 * Opens the given bz2 compressed file for reading and decompresses the file,
 * returning an array of the lines of the file. A line is denoted by the
 * separator argument.
 *
 *    Bzip2::Writer.open('file'){ |f| f << "a\n" << "b\n" << "c\n\nd" }
 *
 *    Bzip2::Reader.readlines('file')      # => ["a\n", "b\n", "c\n", "\n", "d"]
 *    Bzip2::Reader.readlines('file', 'c') # => ["a\nb\nc", "\n\nd"]
 *
 * @param [String] filename the path to the file to read
 * @param [String] separator the character to denote a newline in the file
 * @see Bzip2::Reader#readlines
 * @return [Array] an array of lines for the file
 * @raise [Bzip2::Error] if the file is not a valid bz2 compressed file
 */
static VALUE bz_reader_s_readlines(int argc, VALUE *argv, VALUE obj) {