[RFE] support an exclude list

[vbatts]

Both by golang API and by command line flags.

Upstream as -X <exclude-file>:

-X exclude-file    The specified file contains fnmatch(3) patterns match-
                   ing files to be excluded from the specification, one
                   to a line.  If the pattern contains a `/' character,
                   it will be matched against entire pathnames (relative
                   to the starting directory); otherwise, it will be
                   matched against basenames only.  Comments are permit-
                   ted in the exclude-list file.

This will come in handy for some archives that are using layer-like entries that have file entries that whiteout markers, and will not exist as files once extracted.