Mojo+NaCl: Move generated code to mojo/nacl.

Mojo+NaCl: Move generated code to mojo/nacl.

This change moves generated code for Mojo support in NaCl from mojo/monacl to
mojo/nacl. This makes the target directory more consistent across GYP and GN
builds.

An upcoming change for IRT support will generate a header, which will need a
consistent path (relative to include_dirs) across build systems.

An earlier version of this change failed to update
mojo/mojo_nacl_untrusted.gyp, causing clean builds to fail. I've confirmed
that this change builds correctly with a clean build.

BUG=454466
TEST=clobber, then build

Committed: https://crrev.com/8802d7dd2d30ca90dc834089cb871c5f68b76343
Cr-Commit-Position: refs/heads/master@{#314811}

[teravest, 2015-02-04 21:10:45]

teravest@chromium.org changed reviewers:
+ jamesr@chromium.org, ncbray@chromium.org

[jamesr, 2015-02-04 23:22:01]

lgtm

[Nick Bray (chromium), 2015-02-04 23:34:36]

General LGTM. Relying on Jame's and your judgement for the details, not
functioning 100% right now.

[teravest, 2015-02-05 15:21:36]

The CQ bit was checked by teravest@chromium.org

[commit-bot: I haz the power, 2015-02-05 15:21:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/881933004/1

[commit-bot: I haz the power, 2015-02-05 15:25:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-05 15:26:54]

Patchset 1 (id:??) landed as
https://crrev.com/8802d7dd2d30ca90dc834089cb871c5f68b76343
Cr-Commit-Position: refs/heads/master@{#314811}