[Rd] Bugs due to naive copying of list elements

[Radford Neal]

Several bugs are present in R-2.15.3 and R-alpha due to
naive copying of list elements.

The bug below is due to naive copying in subset.c (with
similar bugs for matrices and arrays):

a<-list(c(1,2),c(3,4),c(5,6))
b<-a[2:3]
a[[2]][2]<-9
print(b[[1]][2])

Naive copying in mapply.c leads to the following bug:

X<-1+1
f<-function(a,b) X
A<-mapply(f,c(1,2,3),c(4,5,6),SIMPLIFY=FALSE)
print(A)
X[1]<-99
print(A)

Similar bugs exist in eapply, rapply, and vapply.