Add taint-tracking for packages inside text/*

[gagliardetto]

codebox commands:

codebox --out-dir=./generated/latest --pkg=/usr/local/go/src/text/scanner --http
codebox --out-dir=./generated/latest --pkg=/usr/local/go/src/text/tabwriter --http
codebox --out-dir=./generated/latest --pkg=/usr/local/go/src/text/template --http

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Part of #167

[smowton]

Needs tests, otherwise looks good! I'll be testing these to see what impact they have on lgtm.com over the course of this week.

[gagliardetto]

Awesome! Thanks.

[smowton]

We'll need to make sure the various escaper functions that are now generally considered taint conductors are properly considered sanitisers by the queries that care about a particular sort of injection, but I didn't see many false positives so we're likely in a good state. LGTM.