Non-GNU libc support

Currently, the library only works 100% of the time when installed on a glibc system. However, some people use other libcs such as musl, so it'd be nice to support them. At the moment, an LD_PRELOAD fallback is used on such systems instead of /etc/ld.so.preload, which leads to inconsistent support. This issue was created to track progress and discuss possible solutions.

Shell support:

• POSIX
• fish (95a2657b)
• Other

Compositor support:

• GNOME Shell
• X.org
• Other

Display manager support:

• GDM
• Other