Factor out toolset definitions in a separate gypi file

That way, third-party libraries use the correct toolset settings.

BUG=v8:2745
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/18846002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15585 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Type::GetName(...) for inspecting Types in the debugger

BUG=
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/18587007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15586 ce2b1a6d-e550-0410-aec6-3dcde31c8c00