src/filemanager/mountlist.c: recognize fuse.portal as dummy file system.

Sync with gnulib 9a38d499ca16f2f4304992eb1ab0894cd0b478e1.

Add "fuse.portal" as a dummy file system (used in flatpak
implementations).

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

src/filemanager/mountlist.c

@@ -205,6 +205,7 @@
    || strcmp (Fs_type, "debugfs") == 0          \
    || strcmp (Fs_type, "devpts") == 0           \
    || strcmp (Fs_type, "fusectl") == 0          \
+   || strcmp (Fs_type, "fuse.portal") == 0      \
    || strcmp (Fs_type, "mqueue") == 0           \
    || strcmp (Fs_type, "rpc_pipefs") == 0       \
    || strcmp (Fs_type, "sysfs") == 0            \