Update sdk to sourcemod maintained version

[sapphonie]

These sdks are maintained by the Sourcemod team, meaning that it's going to be significantly easier to update TFTrue if a tf2 update comes along, as other coders rely on these sdks as well.

[sapphonie]

Also, you should consider enabling building with optimized debug syms.

TFTrue still tends to crash, randomly, a lot. Enabling syms would make debugging crash dumps so much easier.

[sapphonie]

Honestly don't merge this as is. Itd be better using something like https://github.com/TF2-DMB/hl2sdk-tf2, since alliedmodders tf2 branch is STILL out of date on a lot of stuff, which is likely why my tftrue fork still tends to crash