CLEANUP: assorted typo fixes in the code and comments

This is 14th iteration of typo fixes
diff --git a/reg-tests/cache/vary.vtc b/reg-tests/cache/vary.vtc
index be79b6a..fc2c445 100644
--- a/reg-tests/cache/vary.vtc
+++ b/reg-tests/cache/vary.vtc
@@ -193,7 +193,7 @@
        # This request matches the cache entry for the request above, despite
        # matching the `accept-encoding` of the first request because the
        # request above only has the `identity` encoding which is implicitly
-       # added, unless explicitely forbidden.
+       # added, unless explicitly forbidden.
        txreq -url "/accept-encoding" -hdr "Accept-Encoding: first_value"
        rxresp
        expect resp.status == 200