Refine privacy error messages to be more accurate

This stops labeling everything as "is private" when in fact the destination may
be public. Instead, the clause "is inaccessible" is used and the private part of
the flag is called out with a "is private" message.

Closes #9793
Fix an off-by-one in managed::refcount

This fixes a bug I accidentally introduced in #9922
Remove jemalloc from the runtime

As discovered in #9925, it turns out that we weren't using jemalloc on most
platforms. Additionally, on some platforms we were using it incorrectly and
mismatching the libc version of malloc with the jemalloc version of malloc.

Additionally, it's not clear that using jemalloc is indeed a large performance
win in particular situtations. This could be due to building jemalloc
incorrectly, or possibly due to using jemalloc incorrectly, but it is unclear at
this time.

Until jemalloc can be confirmed to integrate correctly on all platforms and has
verifiable large performance wins on platforms as well, it shouldn't be part of
the default build process. It should still be available for use via the
LD_PRELOAD trick on various architectures, but using it as the default allocator
for everything would require guaranteeing that it works in all situtations,
which it currently doesn't.

Closes #9925
auto merge of #9930 : alexcrichton/rust/refcount-tests, r=thestinger

This fixes a bug I accidentally introduced in #9922
Make fields in std::comm private
auto merge of #9935 : reedlepee123/rust/my_new_branch, r=bstrie
auto merge of #9933 : alexcrichton/rust/no-jemalloc, r=brson

As discovered in #9925, it turns out that we weren't using jemalloc on most
platforms. Additionally, on some platforms we were using it incorrectly and
mismatching the libc version of malloc with the jemalloc version of malloc.

Additionally, it's not clear that using jemalloc is indeed a large performance
win in particular situtations. This could be due to building jemalloc
incorrectly, or possibly due to using jemalloc incorrectly, but it is unclear at
this time.

Until jemalloc can be confirmed to integrate correctly on all platforms and has
verifiable large performance wins on platforms as well, it shouldn't be part of
the default build process. It should still be available for use via the
LD_PRELOAD trick on various architectures, but using it as the default allocator
for everything would require guaranteeing that it works in all situtations,
which it currently doesn't.

Closes #9925
Document traits and Default about format! better

Closes #9865
Closes #9808
Remove the fmt! syntax extension

It lived a good life, but its time has come. The groundwork is set for the
official transition after the next snapshot (removal of XXX2 macros)
auto merge of #9856 : alexcrichton/rust/privacy-errors, r=huonw

This stops labeling everything as "is private" when in fact the destination may
be public. Instead, the clause "is inaccessible" is used and the private part of
the flag is called out with a "is private" message.

Closes #9793
auto merge of #9919 : alexcrichton/rust/fmt-begone, r=huonw

It lived a good life, but its time has come. The groundwork is set for the
official transition after the next snapshot (removal of XXX2 macros)
rustpkg: Make rustpkg tests stop comparing dates

Instead of scrutinizing modification times in rustpkg tests,
change output files to be read-only and detect attempts to write
to them (hack suggested by Jack). This avoids time granularity problems.

As part of this change, I discovered that some dependencies weren't
getting written correctly (involving built executables and library
files), so this patch fixes that too.

This partly addresses #9441, but one test (test_rebuild_when_needed)
is still ignored on Linux.
rustc: Check that the output file is writeable before linking

This is because on Linux, the linker will silently overwrite
a read-only file.
rustpkg: invoke touch with a portable set of args
auto merge of #9437 : catamorphism/rust/rustpkg-dates, r=alexcrichton

r? @alexcrichton On most platforms, the time granularity is 1 sec or more, so comparing
dates in tests that check whether rebuilding did or didn't happen leads
to spurious failures. Instead, test the same thing by making an output
file read-only and trapping attempts to write to it.
auto merge of #9938 : alexcrichton/rust/fmtdox, r=huonw

Closes #9865
Closes #9808
Allow fail messages to be caught, introduce Any trait