Files
greatroar 3e24d82513 lib/fs: Optimize UnicodeLowercase (#6979)
Most notably, it now detects all-lowercase files and returns these
as-is. The tests have been expanded with two cases and are now used
as a benchmark (admittedly a rather trivial one).

name                           old time/op    new time/op    delta
UnicodeLowercaseMaybeChange-8    4.59µs ± 2%    4.57µs ± 1%    ~     (p=0.197 n=10+10)
UnicodeLowercaseNoChange-8       3.26µs ± 1%    3.09µs ± 1%  -5.27%  (p=0.000 n=9+10)
2020-09-11 09:16:10 +02:00
..
2019-11-10 10:16:10 +01:00