Fix for PR#15282.

git-svn-id: https://svn.r-project.org/R/trunk@62649 00db46b3-68df-0310-9c12-caf00c1e9a41
vector(*, length):  length must be "double" for long vectors;  
thanks to Herve Pages


git-svn-id: https://svn.r-project.org/R/trunk@62651 00db46b3-68df-0310-9c12-caf00c1e9a41
is.vector(symbol, "name") == TRUE

git-svn-id: https://svn.r-project.org/R/trunk@62653 00db46b3-68df-0310-9c12-caf00c1e9a41