Fix some comments in the code reviews
Fix minor comments from the auth_quant code review.

This commit fixes the Base64W parsing in auth/lexer.go and adds a regression
test to catch this problem in the future. It also fixes some minor comments.
Fix minor problems from the datalog-guard code review.

This commit removes a redundant check, adds a comment, and fixes two minor
formatting problems (not related to the datalog guard code review but included
in this commit anyway).
Remove completed auth_quant and datalog code reviews