Turn -Wmax-tokens off by default
On the one hand, one might interpret the use of the max-token pragmas or
-fmax-tokens flag as an opt-in to the warning. However, in Chromium
we've found it useful to only opt in selected build configurations, even
though we have the pragmas in the code. For that reason, we think it
makes sense to turn it off by default.
Differential revision: https://reviews.llvm.org/D80014