fixes for Box<[T]>

The pointer in the slice must not be null, because enum representations
make that assumption. The `exchange_malloc` function returns a non-null
sentinel for the zero size case, and it must not be passed to the
`exchange_free` lang item.

Since the length is always equal to the true capacity, a branch on the
length is enough for most types. Slices of zero size types are
statically special cased to never attempt deallocation. This is the same
implementation as `Vec<T>`.

Closes #14395
Avoid ever constructing cyclic types in the first place, rather than detecting them in resolve. This simplifies logic elsewhere in the compiler. cc #5527
Prefer lualatex, xelatex, pdflatex, in that order. #12804
reintroduce manual link in doc index

whoops

Fixes https://github.com/rust-lang/rust/pull/16827#issuecomment-55160273
Fix vector terminology in the manual.

fixes #17148
Remove dependency on GCC's LTO linker plugin, since Rust does its' own LTO.
auto merge of #17110 : thestinger/rust/dst, r=cmr

The pointer in the slice must not be null, because enum representations
make that assumption. The `exchange_malloc` function returns a non-null
sentinel for the zero size case, and it must not be passed to the
`exchange_free` lang item.

Since the length is always equal to the true capacity, a branch on the
length is enough for most types. Slices of zero size types are
statically special cased to never attempt deallocation. This is the same
implementation as `Vec<T>`.

Closes #14395
auto merge of #17139 : brson/rust/lualatex, r=alexcrichton

Bugs in pdflatex (#12804) are preventing the guide from landing (https://github.com/rust-lang/rust/pull/16657). This solves the immediate problem by changing the build system to prefer lualatex, xelatex to pdflatex (which is apparently obsolete). Because the xelatex on the snapshot bot seems to completely ignore the `-output-directory` option, I also had to frob the makefiles a bit for that case.
auto merge of #17157 : nikomatsakis/rust/occurs-check, r=pcwalton

Avoid ever constructing cyclic types in the first place, rather than detecting them in resolve. This simplifies logic elsewhere in the compiler, in particular on the trait reform branch.

r? @pnkfelix or @pcwalton 

cc #5527
auto merge of #17153 : steveklabnik/rust/add_link_to_manual, r=sfackler

whoops

Fixes https://github.com/rust-lang/rust/pull/16827#issuecomment-55160273
Append target-specific tools directory ($(RUST)/bin/rustlib/<triple>/bin/) to PATH during linking,
so that rustc can invoke them.
Update license notice.
Package rustc's mingw dependencies into Windows installer.
gcc, ld, ar, dlltool, windres go into $(RUST)/bin/rustlib/<triple>/bin/
platform libraries and startup objects got into $(RUST)/bin/rustlib/<triple>/lib/
auto merge of #17154 : steveklabnik/rust/array_clarification, r=huonw

fixes #17148
auto merge of #16957 : vadimcn/rust/package-gcc, r=brson

Package rustc's mingw dependencies into Windows installer to avoid requiring a separate mingw install.

Closes #11782
Fix bug in padding unicode, #17105.