#1778 standardised using starting index, to fix incorrectly mapped sourcemaps

Fixes #1778.

Appears that there is already convention to use the starting index for most of the nodes, just a couple had not implemented it correctly, or only half implemented it (ie. had index set but still used i). This fixes that to ensure consistency and produce correct sourcemaps.

It does break the sourcemap test because that test tests against a previously generated sourcemap which contains incorrect mappings, rookie testing error I'll leave that to the person that created the rookie test to fix.

Would suggest using http://sokra.github.io/source-map-visualization/ to test sourcemaps.