map_trees deals with both string and table trees

Fixes #178
Several updates:
1) will search the system path for Lua interpreter if no location is found. Only then the ancient defaults will be checked.
2) if /LUA is provided, it will only look there, and fail if not found instead of falling back to the defaults
3) if no interpreter found, it is not automatically installed. Only with explicit /L switch the included interpreter is installed
Merge branch 'master' of github.com:Tieske/luarocks into win_install_checkpath

Conflicts:
	install.bat
fix: registry import with filename containing spaces
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