Copy src/third_party/NSIS to deps/third_party/NSIS

This is in preparation for updating native_client/DEPS and then
removing the old name.

BUG= none
TEST= none

git-svn-id: svn://svn.chromium.org/native_client/trunk/deps/third_party/NSIS@7071 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2