fsck: use xmalloc, warn & err and new usage

fsck: use xmalloc, warn & err and new usage

All compler errors reported by -Wall -Wextra -pedantic are fixed.

The patch also makes fsck to use xalloc instead of it's own malloc.
That will make fsck to exit, which could be good thing, at sections
where it previously did not.

Almost all print outs where touched, where various printfs where
converted to warn or err messages.

Finally theres a fix to counter wrap bug that could (very unlikely)
manifest itself if an user specifies same flag exactly UINT_MAX times.

[kzak@redhat.com: - coding style
                  - define XALLOC_EXIT_CODE
                  - use verbose++ in main()]

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Karel Zak <kzak@redhat.com>