map_trees deals with both string and table trees

Fixes #178
Allow the wrapper scripts to keep working even if LuaRocks is uninstalled
(or if one is building them to run in another box without LuaRocks,
for example, in cross-compiling scenarios).
Merge branch 'master' of github.com:keplerproject/luarocks
Merge pull request #179 from akfidjeland/bugfix-deps-mode-order

map_trees deals with both string and table trees
Merge pull request #181 from Tieske/win_install_checkpath

Search system path for Lua install instead of ancient defaults
Remove incompatibility in the sed command, as reported in the Lua mailing list.
Merge branch 'master' of github.com:keplerproject/luarocks
Merge branch 'master' of https://github.com/keplerproject/luarocks into command_quoting