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