The correct result is 2*%pi. This is a new bug appearing in version 5.21.1. Previous
versions (<= 5.20.1 ) return just the integral expression unevaluated, which is fair enough, but
most importantly is not a wrong result.
Maxima version: 5.21.1
Maxima build date: 8:13 4/26/2010
Host type: i686-pc-mingw32 also on linux system (fedora11)
Lisp implementation type: GNU Common Lisp (GCL) also with cmucl
Lisp implementation version: GCL 2.6.8 also with cmucl 19f