Fix NEWS.txt syntax to please AsciiDoc

Yet another thing AsciiDoc isn't good at.
Do not rely on pids being unique

Based on a patch by Mike Frysinger <vapier@gentoo.org>:

"Linux supports creating pid namespaces cheaply and running processes
inside of them. When you try to share a single cache among multiple such
runs, the fact that the code relies on pid numbers as globally unique
values quickly fails. Instead, switch to standard mkstemp to generate temp
files for us."
Don't try to reset a non-existing stats file

This avoids "No such file or directory" messages in the ccache log when the
cache directory doesn't exist.