Use libdl to get symbols for backtraces

Use libdl to get symbols for backtraces

With this patch, it'll look like this:

$ out/x64.optdebug/d8 --expose-trigger-failure test/mjsunit/mjsunit.js test/mjsunit/verify-assert-false.js

==== C stack trace ===============================

 1: V8_Fatal
 2: v8::internal::FunctionCallbackArguments::Call(void (*)(v8::FunctionCallbackInfo<v8::Value> const&))
 3: 0x727ced
 4: 0x72b6ba
 5: 0x188c7f607f9b

BUG=none
R=svenpanne@chromium.org
LOG=y

Committed: https://crrev.com/843634994fce8da65323d3ba046d32aefd6eba1a
Cr-Commit-Position: refs/heads/master@{#27318}

[jochen (gone - plz use gerrit), 2015-03-19 15:18:44]

jochen@chromium.org changed reviewers:
+ jkummerow@chromium.org

[jochen (gone - plz use gerrit), 2015-03-19 15:18:44]

+jakob ptal

[Jakob Kummerow, 2015-03-19 15:38:34]

Awesome. LGTM.

[jochen (gone - plz use gerrit), 2015-03-19 15:38:58]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-03-19 15:39:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1018313003/20001

[commit-bot: I haz the power, 2015-03-19 15:43:26]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-19 15:43:56]

Patchset 2 (id:??) landed as
https://crrev.com/843634994fce8da65323d3ba046d32aefd6eba1a
Cr-Commit-Position: refs/heads/master@{#27318}