be consequent in requiring an existing directory

Before the fix sxcp -r sx://sth /tmp/dir/ would require /tmp/dir/ to be
created but sxcp -r sx://sth /tmp/dir would happily create the directory.

This commit makes the behaviour consistent, however the side effect is
that -r will not work nicely when copying single files.

The other solution is to go back to the old approach and create the
target dirs automatically.
pass proper sxf_handle to filter's configure
sqlite: print location of WAL_RETRY on SQLITE_PROTOCOL
Do not stop upload if 0-sized file is being transferred
Must call sqlite3_initialize before calling sqlite3_test_control

If sqlite3 is built with THREAD_SAFE=1 it must be called to prevent a null
deref.
drop valgrind.h: its not needed
Move SQLite3 to 3rdparty, and add flag to use system version
Introduce --with-system-libs flag (bb #457)
move sxserver/sxsetup to server/sxscripts/
make sxscripts work with --disable-sxhttpd too
move sx scripts to sbin
BSD sed doesn't have -i
don't use \0 in sed
sxserver: add $SX_FCGI_OPTS
sxvol cosmetics (bb#491)
bump hashfs version
make some errors non-fatal when iterating over local files (bb#436)
only verify local files when iterating
sxcp progress cosmetics

Remove progress bar when transfer finished.
Do not use sxi_notice() when sxi_xfer_set_file() fails.
Change error message printed on file transfer flush fail.
fix run