/*
 * call-seq:
 *    conn.block( [ timeout ] ) -> Boolean
 *
 * Blocks until the server is no longer busy, or until the 
 * optional _timeout_ is reached, whichever comes first.
 * _timeout_ is measured in seconds and can be fractional.
 * 
 * Returns +false+ if _timeout_ is reached, +true+ otherwise.
 * 
 * If +true+ is returned, +conn.is_busy+ will return +false+
 * and +conn.get_result+ will not block.
 */
static VALUE
pgconn_block( int argc, VALUE *argv, VALUE self ) {