fstools: update to git HEAD
f0fc66a libfstools: check for overlay mounting errors
128ecaf Update / fix extroot comments
8a0ba3b libfstools: get rid of "extroot_prefix" global variable
649cd3f libfstools: use variable for overlay mount-point
922f1b3 libfstools: avoid segfault in find_mount_point
ce5eacb libfstools: mtd: improve error handling
898b328 blockd: restore device_move semantics
0917d22 block: don't probe mtdblock on NAND (with legacy exceptions)
Signed-off-by: Daniel Golle <daniel@makrotopia.org>