Add new GPLv3 license text and acknowledgements.
Add licenses for GPLv2 and GPLv3.
Update license headers for AMXX core.
Update license headers for compiler.
Update license headers for cstrike modules.
Update license headers for dod modules.
Update license headers for engine module.
Update license headers for fakemeta module.
Update license headers for fun module.
Update license headers for geoip module.
Update license headers for hamsandwich module.
Update license headers for mysql module.
Update license headers for ns module.
Update license headers for nvault module.
Update license headers for regex module.
Update license headers for socket module.
Update license headers for sqlite module.
Update license headers for tfcx module.
Update license headers for ts modules.
Update license headers for plugins and includes.