[sldev] GCC 4.x warning patches.

[lists.secondlife.com at trap.wereanimal.net]

I've created snow-193 through 195 with patches that fixes the warnings. I did 
this when I discover there was a cmake hack that checked for GCC 4.3 and 
disabled some warnings instead of fixing the code. So I removed the check and 
started to fix the code.

I've split the patch into three parts for easy review and hopefully they will 
get added.

-- Techwolf Lupindo