Add support for startup data (snapshot) compression.

Add support for startup data (snapshot) compression.

This is for mobile platforms where application footprint size is
important. To avoid including compression libraries into V8, we assume
that the host machine have them (true for Linux), and rely on embedder
to provide decompressed data.

Currently, only snapshot data can be comressed. It is also possible to
compress libraries sources, but it is more involved and will be
addressed in another CL.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6901090

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7724 ce2b1a6d-e550-0410-aec6-3dcde31c8c00