Joinable pthreads need to be either joined or detached and we no
longer join with the scheduler threads.

Changes to resolve and typeck. Still nothning working yet.

fixed memmove. were using memcpy due to copy paste error

* -g or --mode=user to create/use .cargo under $HOME
* -G or --mode=system to create/use .cargo under sysroot
* by default, `cargo` uses .cargo under current working directory

Enough to be able to compile librustc with --monomorphize.

Issue #1736

Closes #1717

Issue #1736

This function creates a new scheduler with a specified number of threads and
immediately executes a task on it. The scheduler is configured to terminate
when the task dies. This is the minimum API necessary to enable blocking C
calls.