fuse2fs, fuse4fs: Fix MacFuse compatibility issue
fuse2fs: fix uninitialized variable warnings
libsupport: fix gcc -Wall warnings
libsupport: remove the LIST_HEAD macro from list.h
fuse[24]fs: suppress clang warnings which were breaking the github CI
libsupport: don't use bzero in cache.c
configure.ac: fix disable fuse2fs/fuse4fs by default path
libsupport: drop xbitops.h and define fls() if necessary