Issue #6419: Better clang version detection for Apple Clang

Apple Clang uses different version numbering than "regular" clang, but
it also provides the "regular" version it's based on. Update the sed
pattern to pull out this "regular" version number instead of the Apple
version number.
Make AtomicPtr use *mut, instead of ~
Add AtomicOption type
Add some documentation
librustc: Allow intra-crate start functions, for runtimeless operation.
make the memcpy/memmove intrinsics higher-level

This allows them to make use of the type's alignment, instead of being
pessimistic and assuming it is only 1.
C++0x -> C++11
add memset32/memset64
use uninit for cast::transmute_copy
add an align parameter to call_memcpy
make transmute_copy use memcpy, and inline it
inline bump_box_refcount
Add a short section on ARC
mark unique pointer parameters as noalias

Closes #6749
Use passing by-value in gmtime, mktime

Per the recommendation of the now-removed FIXME.
Increment copyright year of time.rs
syntax highlight code examples in docstrings
extra: Add reserve and reserve_at_least to extra::deque

As called for in #4994
Add xfail'd test for #6762.
Change `alt` to `match` in filenames.