[Rd] acf segfault (PR#7771)

[davidhughjones at gmail.com]

Test case:
z <- ts(matrix(rnorm(200),10,20), start=c(1961,1))
acf(z,lag.max=1)

This segfaults for me. Maybe it shouldn't?
cheers
dave

--please do not edit the information below--

Version:
 platform = i386-pc-linux-gnu
 arch = i386
 os = linux-gnu
 system = i386, linux-gnu
 status =
 major = 2
 minor = 0.1
 year = 2004
 month = 11
 day = 15
 language = R

Search Path:
 .GlobalEnv, package:methods, package:stats, package:graphics,
+package:grDevices, package:utils, package:datasets, Autoloads, package:base