files: Move regular files handling code to files-reg

Instead of spreading regular files handling code over
files.c and cr-dump.c move it to files-reg.c.

This allows to extend regular file handling code in
future without disturbing other source files and
make code logically coupled, where files.c is mostly
a place for general file handling code unrelated to
file type specifics.

While mostly it was code tossing there is some change
I have to notice -- the structure ghost_file was previously
declared in two paces cr-dump.c and files.c, in cr-dump.c
it was used for dumping while in files.c it was used
for restore. The structure had different members.

So to resolve this conflict the ghost_file structure
was renamed to ghost_file_dumpee.

Nothing else is changed.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>