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.
Unhide lines in rustdoc's doc -- Closes #11645
Add a limited prim type lookup for safer const expr evaluation
Add test for issue 6157
Remove unused imports.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Prefix _ to unused variables.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Append ; to #[allow(dead_code)].

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
remove a layer of indirection from most intrinsics
Rename std::borrow to std::reference.

Fixes #11814
Remove double-use of logging.
Remove seldom-used std::reference functions.
Add test case for issue #11681
Fix inconsistency in tutorial.md

Text refers to "the type shown earlier", when the type in
question was not in fact shown earlier.  I assume this is
an artifact of an earlier revision.
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)
Make shift_ref and mut_shift_ref return Option instead of failing
Make pop_ref and mut_pop_ref return Option instead of failing on empty vectors