BUG/MINOR: debug: properly use long long instead of long for the thread ID

I changed my mind twice on this one and pushed after the last test with
threads disabled, without re-enabling long long, causing this rightful
build warning.

This needs to be backported if the previous commit ff64d3b027 ("MINOR:
threads: export the POSIX thread ID in panic dumps") is backported as
well.
2 files changed