cmogstored 1.8.1 - use default system stack size

This release fixes a segfault on some systems/toolchains where
our per-thread stack size was too small.  Given the prevalance
of 64-bit systems nowadays, using a small stack is unlikely to
yield any benefits.

Users on 32-bit systems who wish to continue with a minimal
stack should use "ulimit -s" in startup scripts or configure
their process manager appropriately (e.g. setting the
"LimitSTACK" directive in described in systemd.exec(5)).

Thanks to Xiao Yu <xyu@automattic.com> for reporting and
testing at our public mailbox:
https://yhbt.net/cmogstored-public/CABfxMcW+kb5gwq3pSB_89P49EVv+4UkJXz+mUPQTy19AdrwbAg@mail.gmail.com/T/