Revert "Merge branch 'rust-servo' into rust-0.8: Use SiegeLord/RustCMake for CMake-rust integration. fixes #24."

This reverts commit a8b50a8100914e148b9f4dbfa69cdc0a0f8b4996, reversing
changes made to 5c88920625aa9a1c22cd401ae837f6ad3e9aa424.