Some xzcat cleanup by Isaac Dunham.
Partial cleanup of find

- Remove unnecessary headers
- dump_node is not used anywhere
- exec_buf is unused
- Replace SUCCESS with 1 and simplify code accordingly
- a==0 -> !a
- Simplify an incremation pattern using pre-increments
- Add static keyword to functions
- Make error messages print to stderr
Redo find's indenting from tabs to two spaces.
More cleanup on find.
More of same.
Actually, it's not quite the same:
-use crc_init(xz_crc32_table,1) -- I guessed on this one based on a match between magic constants, then tested it. First try was wrong, but this works.
(This is the sole difference in terms of actual _code_, as opposed to cleaning up defines and the like--here, it adds 48 bytes to final size if xzcat is the only toy, but drops 32 bytes if bzcat is also enabled...)
-Move some crc64 code to where the comments are. This puts them near the area where they're used.
-Remove some relics of separate files (we had half a dozen "this file is in the public domain" notices, a duplicate include, and used extern declarations for functions in the samefile)
More xzcat cleanup.