#4020 various limit bugs with exp(%i*x)

[Stavros Macrakis]

limit(x*exp(%i*x),x,inf) => und; should be infinity
limit(x+x*exp(%i*x),x,inf) => inf; should be infinity
limit(1+x*exp(%i*x),x,inf) => 1; should be infinity

[Barton Willis]

Another:

(%i1)   limit(sin(x) + x*cos(x),x,inf);
(%o1)   0

[David Scherfgen]

Correction: limit(x+x*exp(%i*x),x,inf) should be und. x+x*exp(%i*x) is equivalent to 2*x*cos(x/2)*exp(%i*x/2), which vanishes at every odd multiple of %pi.

[David Scherfgen]

Fixed by commit [5fd39c].