IDL: fix handling of non-decimal and unsigned default values

IDL: fix handling of non-decimal and unsigned default values

The operation Document.createNodeIterator() has the argument
  optional unsigned long whatToShow = 0xFFFFFFFF
which exposes a few problems in the IDL scripts.

First, "0xFFFFFFFF" is rejected by int(x) in default_node_to_idl_literal().
Using int(x, base=0) solves this; int() then selects base 8, 10 or 16
automatically.

Second, for unsigned integer types, we should add a 'u' suffix to the
C++ integer literal, or it's not guaranteed to be valid, in particular not
in 32-bit builds. This is implemented by adding a utility function on
IdlType for converting an IdlLiteral to a C++ expression. This utility
function is also a natural place to add type compatibility checks in the
future, so include a FIXME about that.

BUG=258153
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176926

[Jens Widell, 2014-06-25 12:13:45]

PTAL

[haraken, 2014-06-25 12:18:54]

LGTM

[Jens Widell, 2014-06-25 12:30:44]

The CQ bit was checked by jl@opera.com

[commit-bot: I haz the power, 2014-06-25 12:31:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jl@opera.com/352133002/1

[commit-bot: I haz the power, 2014-06-25 13:36:15]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/13531)

[commit-bot: I haz the power, 2014-06-25 14:41:07]

Change committed as 176926