extra: %U support in time::strftime

Fixes #2350
avoid alloca in with_overflow intrinsics

This is pointless, since it's just used to load an `undef` value and
never touched again.
Add an implementation of FromStr for ~str and @str

This fixes an issue for APIs that return FromStr. Before this change,
they would have to offer a seperate function for returning the source
string.
treat uninhabited enums as voidish
make small (<= size_of::<int>()) enums immediate

C-like enums are excluded from this for now, because the code paths
specific to them need to be changed.

    fn foo() -> Option<~int> { Some(~5) }

Before:

    ; Function Attrs: uwtable
    define void @_ZN3foo18hdec6e36682b87eeaf4v0.0E(%"enum.std::option::Option<~int>[#1]"* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      %2 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw17h56c543b77f9b78aY11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
      %3 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %2 to i64*
      store i64 5, i64* %3, align 8
      %4 = getelementptr inbounds %"enum.std::option::Option<~int>[#1]"* %0, i64 0, i32 0
      store i64* %3, i64** %4, align 8
      ret void
    }

After:

    ; Function Attrs: uwtable
    define %"enum.std::option::Option<~int>[#1]" @_ZN3foo18h2cbf6557a3143edah4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      %1 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw18hb1e9dd1beab35edau11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
      %2 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %1 to i64*
      store i64 5, i64* %2, align 8
      %oldret = insertvalue %"enum.std::option::Option<~int>[#1]" undef, i64* %2, 0
      ret %"enum.std::option::Option<~int>[#1]" %oldret
    }
auto merge of #9677 : thestinger/rust/immediate, r=huonw

C-like enums are excluded from this for now, because the code paths
specific to them need to be changed.

    fn foo() -> Option<~int> { Some(~5) }

Before:

    ; Function Attrs: uwtable
    define void @_ZN3foo18hdec6e36682b87eeaf4v0.0E(%"enum.std::option::Option<~int>[#1]"* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      %2 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw17h56c543b77f9b78aY11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
      %3 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %2 to i64*
      store i64 5, i64* %3, align 8
      %4 = getelementptr inbounds %"enum.std::option::Option<~int>[#1]"* %0, i64 0, i32 0
      store i64* %3, i64** %4, align 8
      ret void
    }

After:

    ; Function Attrs: uwtable
    define %"enum.std::option::Option<~int>[#1]" @_ZN3foo18h2cbf6557a3143edah4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      %1 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw18hb1e9dd1beab35edau11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
      %2 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %1 to i64*
      store i64 5, i64* %2, align 8
      %oldret = insertvalue %"enum.std::option::Option<~int>[#1]" undef, i64* %2, 0
      ret %"enum.std::option::Option<~int>[#1]" %oldret
    }
extra: %G, %g and %V support in time::strftime

Fixes #2350
Check enums in missing_doc lint

Closes #9671
auto merge of #9670 : luisbg/rust/strftime, r=alexcrichton
auto merge of #9680 : thestinger/rust/overflow, r=huonw

This is pointless, since it's just used to load an `undef` value and
never touched again.
Highlight line numbers of the lines referred to in the url hash
Prevent source view from wrapping lines
auto merge of #9675 : sfackler/rust/lint, r=alexcrichton

Closes #9671
extra: %W and %+ support in time::strftime

Plus testing added for %X and %x which were supported but not tested.

Working towards #2350
Make source links highlight the entire definition and not just the first line
rustdoc: Generate hyperlinks between crates

The general idea of hyperlinking between crates is that it should require as
little configuration as possible, if any at all. In this vein, there are two
separate ways to generate hyperlinks between crates:

1. When you're generating documentation for a crate 'foo' into folder 'doc',
   then if foo's external crate dependencies already have documented in the
   folder 'doc', then hyperlinks will be generated. This will work because all
   documentation is in the same folder, allowing links to work seamlessly both
   on the web and on the local filesystem browser.

   The rationale for this use case is a package with multiple libraries/crates
   that all want to link to one another, and you don't want to have to deal with
   going to the web. In theory this could be extended to have a RUST_PATH-style
   searching situtation, but I'm not sure that it would work seamlessly on the
   web as it does on the local filesystem, so I'm not attempting to explore this
   case in this pull request. I believe to fully realize this potential rustdoc
   would have to be acting as a server instead of a static site generator.

2. One of foo's external dependencies has a #[doc(html_root_url = "...")]
   attribute. This means that all hyperlinks to the dependency will be rooted at
   this url.

   This use case encompasses all packages using libstd/libextra. These two
   crates now have this attribute encoded (currently at the /doc/master url) and
   will be read by anything which has a dependency on libstd/libextra. This
   should also work for arbitrary crates in the wild that have online
   documentation. I don't like how the version is hard-wired into the url, but I
   think that this may be a case-by-case thing which doesn't end up being too
   bad in the long run.

Closes #9539
auto merge of #9689 : luisbg/rust/strftime, r=alexcrichton

Plus testing added for %X and %x which were supported but not tested.

Working towards #2350
auto merge of #9681 : skade/rust/str-from-str, r=huonw

This fixes an issue for APIs that return FromStr. Before this change,
they would have to offer a seperate function for returning the source
string.
Stop using newtype wrappers in std::rt::io

UnboundedPipeStream is still a newtype since process::set_stdio needs to
look into its internals.

Closes #9667
auto merge of #9693 : sfackler/rust/newtype-removal, r=alexcrichton

UnboundedPipeStream is still a newtype since process::set_stdio needs to
look into its internals.

Closes #9667