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

IRespawnInitiator and InventoryActions are abstract classes, but they
were missing a virtual destructor. Define it, even if it does nothing
and its absence most likely makes no difference other tha causing
warnings during compile.

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