(find_new_file_size): Return size instead of storing through pointer.

(find_new_file_size): Return size instead of storing through pointer.
All callers changed.
(deal_with_sparse): Don't keep reading after read errors.
(finish_sparse_file): Just abort if there is an internal error.
Use error message functions to report errors consistently.
(dump_file): Fix typo: stat_warn and stat_error were interchanged.
Quote file names with colons if possible.
Don't restore access times on directories during incremental dumps
until after dealing with the directory.
If ignoring failed reads, count closedir errors as warnings, not errors.
Fix buffer overrun problem when dumping sparse files.
If ignoring failed reads, count read errors as warnings, not errors.
Use error message functions to report errors consistently.
If ignoring failed reads, count unknown files as warnings, not errors.