Make syslog thread-safe in --disable-gil builds

[colesbury]

Feature or enhancement

The syslog module has two mutable global variables:

cpython/Modules/syslogmodule.c

Lines 71 to 72 in 9dae05e

	static PyObject *S_ident_o = NULL; // identifier, held by openlog()
	static char S_log_open = 0;

We need to protect access to these variables in the --disable-gil builds.

Linked PRs

• gh-117440: Make syslog thread-safe in free-threaded builds #117441