Trouble compiling 1.24.1 on a Linux box with older glibc-dev than 2.32

[minghia]

The file common/althreads.h has a dependency on threads.h which is a C11 addition. Unfortunately threads.h only appeared in glibc releases after 2.32. This means that even though one may have a C++17 compiler such as GCC 9.2.0, althreads.h causes 1.24.1 to fail to build. I did get 1.23.1 to build as it appears to not have the dependency on threads.h.

[kcat]

Commit 563a1c2 tries to use a more robust check to avoid C11 threads/tss_t. I don't know whether it'll work for a given arbitrary system that supports C++17 but not the C11 threads API, but it's worth trying.