Sources here are from luasql git tag 2.7.0
(https://github.com/lunarmodules/luasql/tree/2.7.0)
Some modifications have been done to them:
- Commit 10ed75b36bf909f57b3c1a070dd87669c323cff0 backported
- Fixed compile error on ls_sqlite3.c raw_readparams_table()
  Fix has been submitted to upstream.
- Cleared trailing spaces
  Equivalent patch submitted to upstream.

Only the files needed by freeciv are included here, not entire luasql
source directory hierarchy.
The ls_*.h files are our own additions to use those backends directly.
