code review 147220043: test: migrate remaining tests to run.go

test: migrate remaining tests to run.go

Finishes the work started in CL 144630044.

* bug248 was split into a rundir half (bug248) and an errorcheckdir half (bug248b).
* bug302, bug345, bug369, and bug429 were ported from bash commands to run scripts. bug369 remains disabled.
* bug395 is a test for issue 1909, which is still open. It is marked as skip now and will be usable with compile with run.go when issue 1909 is fixed.

Update issue 1909

Fixes issue 4139.

[josharian, 2014-09-26 20:42:23]

Hello rsc@golang.org, bradfitz@golang.org (cc:
golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go

[josharian, 2014-09-26 20:44:46]

A large but boring CL. Changes to run.go will need updating once CL 144630044
has been submitted.

Not tested on Windows, but I think I've done the path handling carefully enough.

Mailed now in case you want a head start on it. I'll update + ping once CL
144630044 is in.