Let's ensure that we always use the thread-safe strerror_r() function and add
an approriate macro.
Additionally, define SYS*() macros for all log levels. They will use the new
macro and ensure thread-safe retrieval of errno values.
Signed-off-by: 2xsec <dh48.jeong@samsung.com>
[christian.brauner@ubuntu.com: simplify lxc_log_strerror_r macro]
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>