Change the signature for StrNDup to match the implementation.  This mismatch causes problems if attempting to build d8 with readline support.
Change the signature for StrNDup to match the implementation.  This
mismatch causes problems if attempting to build d8 with readline
support.

Review URL: http://codereview.chromium.org/414033

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@3342 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh