add a higher level glob() function to os

this could probably use expansion - it just uses all of the default
options, which is usually what we want, but not always. maybe add a
separate function that takes more options?
glob_t should be public on all platforms
libcore: add N(0,1) and Exp(1) distributions to core::rand.

Sample from the normal and exponential distributions using the Ziggurat
algorithm.
auto merge of #6161 : graydon/rust/glob-retry, r=graydon

This is a retry of pull #5832
mk: minor fix for test.mk to support mutiple target test
rustc: adjust total number of lang items
rustc: fix the fact that trans_lvalue rooted twice
core: add more debugging printouts to borrowing
auto merge of #6162 : graydon/rust/random-retry, r=graydon

Sample from the normal and exponential distributions using the Ziggurat
algorithm.
Take string slices
Use static strings
auto merge of #6127 : gifnksm/rust/impl-clone-for-bigint, r=graydon

implement `Clone` using `deriving(Clone)`.
lang: fix code for maintaining borrow list
rustc: more fix for trans_lvalue rooted twice
syntax: fix up dynamic borrow errors in libsyntax
Add error if RED_ZONE_SIZE doesn't get defined
libcore: Make `ChainIterator` take two different-typed `Iterator`s.
pass along CFLAGS/LINK_FLAGS to libuv

Closes #6142
auto merge of #6173 : sammykim/rust/doc-vec, r=yichoi

I think whether vector element is mutable is decided by whether vector reference is mutable.
Remove 'Local Variable' comments