ICU 4.6 NumberFormat::EStyle enum is gone in ICU 4.8. Adding #if #else to make it work across versions.

There was an ICU cleanup (removing all C++ style enums and replacing them with plain C enums). NumberFormat::EStyle had a draft status (from ICU 4.2) and it was cut. Confusion came up because DateFormat::EStyle is stable and won't be removed.

TEST=Compile Chromium with ICU 4.6 and ICU 4.8
BUG=1561
Review URL: http://codereview.chromium.org/7421003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8701 ce2b1a6d-e550-0410-aec6-3dcde31c8c00