Print all the syntax errors.  Fixes issue 2811.

Change Windows binary removal strategy.
This should keep the temporary files closer to
the binaries they are for, which will make it
more likely that the rename is not cross-device
and also make it easier to clean them up.
Fixes #2604 (as much as we can).

The standard build does not use the go command
to install the go command anymore, so issue 2604
is less of a concern than it originally was.
(It uses the go_bootstrap command to install
the go command.)

Buffer 'go list' output.

R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/5604048