Add early-exit in entity output detour if entity has no classname.
Revert "Disable FireOutput gamedata on TF2 until proper fix is found."

This reverts commit 91ea5ca857f83f0877a230d21b123daa2ff62f4f.
Fix FindStringIndex native not returning INVALID_STRING_INDEX when string not found (bug 6144).
Update CS:GO CSWeaponDrop gamedata.
Add support for building with MSVC 11 and 12 on Windows.