Add timestamps to test stats

Summary: All the tests claim to take 0s when run via fbmake runtests,
so add start and end times to get real numbers.

Also included a cpu time which is displayed with the
--verbose output

Reviewed By: @bertmaher

Differential Revision: D1735237

Signature: t1:1735237:1418397500:13d548f0901ad02d2561c0273aaa06d8827bd5c9
Lower default socket timeout for debugger tests

Summary: Two of the tests in here intentionally wait for a socket to timeout,
and the default of 60 seconds was making test/quick hang for a bit at the end.

Reviewed By: @edwinsmith

Differential Revision: D1736153

Signature: t1:1736153:1418389416:8e513aba6aa953de415d6db2659dfd34dfc7d945
Modify rpoSortCfg to reduce memory usage in refcount-opts

Summary: The old order was specifically designed so exit blocks would appear
last in the RPO order, for optimal codegen. But codegen order is now decided by
vasm's rpo sort so this shouldn't affect it. Anyway, because we were visiting
exit blocks last, their in-states would sit around in a map waiting to be used
until we finished visitng the rest of the blocks. With this new order, we'll
visit exit blocks and then erase their in-state right after visiting the
predecessor. This means the max size of the state map is now O(1) on long
traces with lots of exits blocks, rather than O(nExits).

This exposed a refcount-opts issue where we were depending on the traversal
order to punt in units with unsupported instructions. I changed it to check for
that condition in a better way before even starting the optimization.

Reviewed By: @bertmaher

Differential Revision: D1734625