Stop aggressive inlining.
Stop aggressive inlining.

It's not clear what exactly is happening here, but the Read implementation
for text decoding appears a bit sensitive. Small pertubations in the code
appear to have a nearly 100% impact on the overall speed of ripgrep when
searching UTF-16 files.

I haven't had the time to examine the generated code in detail, but
`perf stat` seems to think that the instruction cache is performing a lot
worse when the code slows down. This might mean that excessive inlining
causes a different code structure that leads to less-than-optimal icache
usage, but it's at best a guess.

Explicitly disabling the inline for the cold path seems to help the
optimizer figure out the right thing.

BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep