Add public version macros.

Add public version macros.

Side note: tools/v8-info.sh seems to have been broken ever
since the move to git.  At least it's not more broken now.

BUG=v8:3075
LOG=y

TEST=./script_test.py

Committed: https://crrev.com/9dac60ad2d38ae934ea37a5e90096cce8d950e08
Cr-Commit-Position: refs/heads/master@{#26873}

[Michael Achenbach, 2015-02-25 15:01:20]

machenbach@chromium.org changed reviewers:
+ ben@strongloop.com, jkummerow@chromium.org

[Michael Achenbach, 2015-02-25 15:01:42]

PTAL. Copy of https://codereview.chromium.org/955963002/

[Michael Achenbach, 2015-02-25 15:27:03]

Guess we're lacking some gyp and gn changes that also need to
be backmerged...

[Jakob Kummerow, 2015-02-25 15:38:01]

lgtm

[Michael Achenbach, 2015-02-26 08:57:15]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-02-26 08:58:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/959713003/1

[commit-bot: I haz the power, 2015-02-26 08:59:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-26 08:59:33]

Patchset 1 (id:??) landed as
https://crrev.com/9dac60ad2d38ae934ea37a5e90096cce8d950e08
Cr-Commit-Position: refs/heads/master@{#26873}