cmfs: make cmfs mount code passing gcc compiling

This patch is the first gcc compiling passed version for cmfs mount
implementation.

Anyway, it does not funcationally work yet. There are many mandatory
routines are implemented as stubs.

More patches will be followed to improve these stub routines.
cmfs: improve patch comments for cmfs/0003-cmfs-implement-early-mount-code.patch

Patch cmfs/0003-cmfs-implement-early-mount-code.patch is refreshed by
quilt, the patch comments should be updated too.