Use an absolute path in test_process_output_fail_to_start

This test is designed to ensure that running a non-existent executable
results in a correct error message (FileNotFound in this case of this
test).  However, if you try to run an executable that doesn't exist, and
that requires searching through the $PATH, and one of the $PATH components
is not readable, then a PermissionDenied error will be returned, instead
of FileNotFound.
Add test for issue 6157
Rename std::borrow to std::reference.

Fixes #11814
Remove double-use of logging.
Remove seldom-used std::reference functions.
auto merge of #11914 : FlaPer87/rust/issue-6157, r=alexcrichton

closes #6157
Implement default type parameters in generics.
auto merge of #11217 : eddyb/rust/generic-default-type-params, r=cmr
auto merge of #11895 : xales/rust/libstd, r=alexcrichton

Fixes #11814
Make size_of, align_of, and element_offset functions return u64 instead of uint in trans::machine (per #5172)
auto merge of #11759 : nathanielherman/rust/master, r=alexcrichton

For #5172
auto merge of #11784 : eminence/rust/fix_run_tests, r=alexcrichton

This test is designed to ensure that running a non-existent executable
results in a correct error message (FileNotFound in this case of this
test).  However, if you try to run an executable that doesn't exist, and
that requires searching through the $PATH, and one of the $PATH components
is not readable, then a PermissionDenied error will be returned, instead
of FileNotFound.

Using an absolute path skips the $PATH search logic in exec, thus by-passing the logic in exec that would have returned a PermissionDenied

In the specific case of my machine, /usr/bin/games was part of $PATH, but my user account wasn't in the games group (thus being unable to read /usr/bin/games)

See the man pages for execv and execve for more details.

I've tested this on Linux and OSX, and I am fairly certain that there will be no problems on Windows
Fix the size of the _Unwind_Exception struct

On OSX 32-bit, the private fields are 5 words long, not 2. I found this
segfaulting before this change, and after this change it no longer segfaulted.
auto merge of #11947 : alexcrichton/rust/osx-unwind, r=brson

On OSX 32-bit, the private fields are 5 words long, not 2. I found this
segfaulting before this change, and after this change it no longer segfaulted.