syntax: Tweak parsing bounds on generics paths

The previous syntax was `Foo:Bound<trait-parameters>`, but this is a little
ambiguous because it was being parsed as `Foo: (Bound<trait-parameters)` rather
than `Foo: (Bound) <trait-parameters>`

This commit changes the syntax to `Foo<trait-parameters>: Bound` in order to be
clear where the trait parameters are going.

Closes #9265
auto merge of #13079 : alexcrichton/rust/colons, r=cmr

The previous syntax was `Foo:Bound<trait-parameters>`, but this is a little
ambiguous because it was being parsed as `Foo: (Bound<trait-parameters)` rather
than `Foo: (Bound) <trait-parameters>`

This commit changes the syntax to `Foo<trait-parameters>: Bound` in order to be
clear where the trait parameters are going.

Closes #9265
_match.rs: prune sub-match tree too aggressively

The `_match.rs` takes advantage of passes prior to `trans` and
aggressively prunes the sub-match tree based on exact equality. When it
comes to literal or range, the strategy may lead to wrong result if
there's guard function or multiple patterns inside tuple.

Closes #12582.
Closes #13027.
rustc: mark references w/anonymous lifetime nocapture

Closes #6751
Address review
auto merge of #13034 : edwardw/rust/match, r=nikomatsakis

The `_match.rs` takes advantage of passes prior to `trans` and
aggressively prunes the sub-match tree based on exact equality. When it
comes to literal or range, the strategy may lead to wrong result if
there's guard function or multiple patterns inside tuple.

Closes #12582.
Closes #13027.
test/run-pass/out-of-stack: prevent tco

We really do *not* want TCO to kick in. If it does, we'll never blow the
stack, and never trigger the condition the test is checking for. To that end,
do a meaningless alloc that serves only to get a destructor to run. The
addition of nocapture/noalias seems to have let LLVM do more TCO, which
hurt this testcase.
auto merge of #13001 : cmr/rust/unnamed-lifetime-nocapture, r=nikomatsakis

Closes #6751