user-specified mount points in inc-recursive mode.

--copy-dest use a temp file when not in in-place mode, and has
various improvments for the code.  I have also "#if 0"ed the code
in the receiver that makes missing directories to see if we can
figure out if it is needed (and if so, what for).

often when overwriting a shorter file.

contents of the module's root directory.

overload.

source path with --relative.

defined.

the generator gets a chance to finish the hard links.

the newer, recommended method.  (Couldn't switch uid_t and gid_t.)

- Got rid of some unneeded blocking_io value twiddling.
- Send --use-qsort to the server if it was specified.

  call it when the server is in setup_protocol().  The function sets
  allow_inc_recurse to 0 if some options won't allow us to support
  an incremental-recursive transfer.
- The server now checks for an 'i' in the -e option from the client
  and zeros out allow_inc_recurse if not found.
- The server reports its inc_recurse determination back to the client.
- The client sets inc_recurse based on the value it gets from the server.

  is going to run in inc_recurse mode or not.
- Verify that the options we received (as a server or as a batch-reader)
  are compatible with the requested inc_recurse mode.

that likes to point out an "if (...)" with a semicolon after it).

symlinks.

no need to comment if a RSYNC_PASSWORD environment variable is set.