This fallback to std::map & std::set for older compilers

Use UNORDERED_SET as an example in decoration and ore biome sets

Use UNORDERED_MAP as an example in nameidmapping

Switch the license to be LGPLv2/later, with small parts still remaining as GPLv2/later, by agreement of major contributors

--HG--
rename : src/licensecomment.txt => licensecomment.txt