Patches: Range insertion for DenseSet; definition of DenseMapInfo<char>

Here are two minor patches. The first adds an insert method to
DenseSet that takes two iterators representing the beginning and
ending of a range of items to insert. I lifted the code verbatim from
DenseMap.h.
The second patch defines DenseMapInfo for chars. This is useful
because DenseSet is implemented as a DenseMap of (Type, char), so
anyone who uses DenseSet has to define DenseMapInfo for char. Let me
know if this definition should go in some place other than DenseMap.h.

Thanks!
Kevin Fan

Index: include/llvm/ADT/DenseSet.h

Looks great, applied:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20090330/075951.html

For future reference, we greatly appreciate patches sent in as attachments instead of inline, this makes it easier to apply. Thanks for the patch!

-Chris