Revert of clang: Suppress a -Wstring-conversion warnings in nspr.

Revert of clang: Suppress a -Wstring-conversion warnings in nspr. (patchset #1 id:1 of https://codereview.chromium.org/754623004/)

Reason for revert:
Build failed:
http://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Linux%20x64/builds/54166
"ERROR: Shared library dependencies changed!"

Unsure if this is the cause, but it looks like a clang roll a few weeks ago caused a similar error message (crbug.com/433065) so seeing if a revert fixes things :) sorry if this is the wrong CL!

Original issue's description:
> clang: Suppress a -Wstring-conversion warnings in nspr.
>
> Do the gn version directly, and roll the nss dep to pick up the gyp version.
>
> BUG=82385
> R=hans@chromium.org
>
> Committed: https://chromium.googlesource.com/chromium/src/+/109b55f5bed033a46f10fd2f50093b82f03586f3

TBR=hans@chromium.org,thakis@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=82385
Committed: https://crrev.com/60f77f2b85674ec3f681cce82b28b83c3beff596
Cr-Commit-Position: refs/heads/master@{#305740}

[vrk (LEFT CHROMIUM), 2014-11-26 00:46:34]

Created Revert of clang: Suppress a -Wstring-conversion warnings in nspr.

[commit-bot: I haz the power, 2014-11-26 00:48:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/758303002/1

[commit-bot: I haz the power, 2014-11-26 00:50:42]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-26 00:52:00]

Patchset 1 (id:??) landed as
https://crrev.com/60f77f2b85674ec3f681cce82b28b83c3beff596
Cr-Commit-Position: refs/heads/master@{#305740}

[Nico, 2014-11-26 00:57:24]

not lgtm

All this change does it change warning flags, it has no effect on code
generation or anything. This isn't a clang roll, it just changes -W flags. I'll
revert this revert.

[Nico, 2014-11-26 00:58:48]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/761683002/ by thakis@chromium.org.

The reason for reverting is: The CL only changed warning flags and had no effect
other than disabling warnings. It doesn't affect code generation, linking, etc.

You can check that the NSS roll only brought in a single cl with a warning flag
change here: https://chromium.googlesource.com/chromium/deps/nss/.