Display the declaration site for "symbol is never used" warnings

[Southclaws]

For example: test.pwn:24 (warning) symbol is never used: "_doReplace" tells me nothing about which library _doReplace is from, it would be nice to raise this warning actually at the declaration point of _doReplace instead of at the end of the script.

I realise the issue here is that the warning function doesn't allow specification of the line/file because that's held in the lexer state so I'm not entirely sure how simple this would be to implement...

[Southclaws]

Well that was quick, and simpler than I thought!