extended pmap with kw args
using closures to test error state
Renasme uv_isopen -> isopen
Add callback for write
Make writes task-blocking by default
Actually look for Scheduler in Base
Don't use blocking writes from the Scheduler
Fix build on Linux
Fix write return value for UTF8
Address Jeff's comments
Make async write close the stream on error
Measure bytes allocated by gc
Merge pull request #3736 from timholy/allocates

Measure number of bytes allocated
Add @bytes to measure allocation during command-line expressions
Update helpdb
Remove redundant infs/nans, provide more useful arg names
Fix copy/paste error in nans cleanup
Consensus nans/infs cleanups
`@bytes` => `@allocated`; only run code once; don't pollute namespace.

Running the code twice is unnecessary since the GC counting is done in
the function body, which must have been compiled already in order to be
running at all. So compilation is already done by the time you're doing
the GC measurements.

This whole approach of evaluating the given expression inside a function
body strikes me as quite likely to behave unexpectedly. It would be nice
to figure out a different way to avoid contamination from compilation.
Fix #3739