Increase system stack size.
auto merge of #8296 : erickt/rust/remove-str-trailing-nulls, r=erickt

This PR fixes #7235 and #3371, which removes trailing nulls from `str` types. Instead, it replaces the creation of c strings with a new type, `std::c_str::CString`, which wraps a malloced byte array, and respects:

*  No interior nulls
* Ends with a trailing null
auto merge of #8425 : dim-an/rust/increase-stack-size, r=brson
Mass rename of .consume{,_iter}() to .move_iter()

cc #7887
Clean up some unused imports in tests
std: merge iterator::DoubleEndedIterator and DoubleEndedIteratorUtil
std: merge Iterator and IteratorUtil
std: Rename Iterator.transform -> .map

cc #5898
std: Iterator.take_ -> .take
std: Iterator.flat_map_ -> .flat_map
std: Iterator.chain_ -> .chain
std: Iterator.last_ -> .last
std: Iterator.len_ -> .len
std: Transform.find_ -> .find
std: fix the non-stage0 str::raw::slice_bytes which broke in a merge
syntax and rustc: fix some warnings