Revert of NaCl: Remove the IRT's Gyp dependency on libsrpc

Revert of NaCl: Remove the IRT's Gyp dependency on libsrpc (patchset #1 id:1 of https://codereview.chromium.org/878623004/)

Reason for revert:

I was a bit too eager about removing the dependency on libsrpc.  I'm
preparing a NaCl change that will make the IRT depend on SRPC again
(https://codereview.chromium.org/883393005/), as a step towards
removing SRPC later.

Unfortunately, untrusted.gypi doesn't support transitive library
dependencies, so it's not enough just for the NaCl side to declare the
dependency on libsrpc.

Original issue's description:
> NaCl: Remove the IRT's Gyp dependency on libsrpc
>
> Since I removed the IRT's calls to NaClSrpcModuleInit() and
> NaClPluginLowLevelInitializationComplete(), the IRT no longer depends
> on SRPC.
>
> BUG=https://code.google.com/p/nativeclient/issues/detail?id=3864
> TEST=build
>
> Committed: https://crrev.com/65a326a734d413e2124c6782b2e32a81ceca74c1
> Cr-Commit-Position: refs/heads/master@{#313664}

BUG=302078
TEST=build

Committed: https://crrev.com/959b409bb77024e26221aadad7bd8afc71cce6d3
Cr-Commit-Position: refs/heads/master@{#314874}

[Mark Seaborn, 2015-02-05 18:08:20]

Created Revert of NaCl: Remove the IRT's Gyp dependency on libsrpc

[Mark Seaborn, 2015-02-05 18:09:33]

@teravest: Please ignore this for now.  That dratted revert tool sent the e-mail
too eagerly.

[Mark Seaborn, 2015-02-05 18:12:53]

mseaborn@chromium.org changed reviewers:
+ jvoung@chromium.org
- teravest@chromium.org

[Mark Seaborn, 2015-02-05 18:20:57]

+jvoung for review.

[teravest, 2015-02-05 18:23:49]

teravest@chromium.org changed reviewers:
+ teravest@chromium.org

[teravest, 2015-02-05 18:23:49]

lgtm

[jvoung (off chromium), 2015-02-05 18:26:06]

lgtm

[Mark Seaborn, 2015-02-05 19:21:44]

The CQ bit was checked by mseaborn@chromium.org

[commit-bot: I haz the power, 2015-02-05 19:22:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/901053008/1

[commit-bot: I haz the power, 2015-02-05 21:01:41]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-05 21:03:35]

Patchset 1 (id:??) landed as
https://crrev.com/959b409bb77024e26221aadad7bd8afc71cce6d3
Cr-Commit-Position: refs/heads/master@{#314874}