Both fusermount.c and mount_util.c use _PATH_MOUNTED, so they should
include <paths.h>, which provides this definition.
This is required for building with the musl C library.
Contributed by Thomas Petazzoni
The libfuse used by OpenIndiana has the same features as libfuse-lite
though requiring some code variants. Merging them simplifies supporting
both.
Variants for OpenIndiana are selected when defining __SOLARIS__
