(Have fun mergining your stuff with this.)

rustc: For stack local derived tydescs, allocate the root tydesc separately from the parameter tydescs. This allows SROA, and consequently inlining, to work.

build: Disable valgrind by default on the Mac. Our suppressions file doesn't even begin to cover the huge stream of errors that dyld generates.

and rust_exit_task_glue calls the rust main.

This is simpler since we only need to setup one frame. It also matches
what ld.so does, so gdb is happy and stops a backtrace at rust_exit_task_glue
instead of continuing past whatever function happened to be before
rust_exit_task_glue is the object file.

This is the rt part and should be merged after the rust0 part.

and rust_exit_task_glue calls the rust main.

This is simpler since we only need to setup one frame. It also matches
what ld.so does, so gdb is happy and stops a backtrace at rust_exit_task_glue
instead of continuing past whatever function happened to be before
rust_exit_task_glue is the object file.

This is only the rustc changes and should be merged first.

as well as a test case

This commit reinstates the requirement that the predicate in a
"check" must be a manifest call to a special kind of function
declared with the new "pred" keyword instead of "fn". Preds must
have a boolean return type and can only call other preds; they
can't have any effects (as enforced by the typechecker).
The arguments to a predicate in a check expression must be
slot variables or literals.

Also added the --batch flag to texi2pdf, as it doesn't really ever
seem useful to drop to the TeX prompt during a build.

Check that the operand in a constraint is an explicit name,
and that the operands are all local variables or literals. Still need
to check that the name refers to a pure function.