AGI: Fix typo in issetv opcode

This fixes bug #3611262
KYRA: (EOB) - add comment in timer_eob.cpp
KYRA: (LOL) - add comment in sprites_lol.cpp
KYRA: (LOL) - fix warning (Unused pointer value) in sprites_lol.cpp
KYRA: (EOB) - fix warning (Logically dead code) in sprites_eob.cpp
KYRA: (EOB) - fix potential null ptr dereference in sprites_eob.cpp
KYRA: (EOB) - add assert in sprites_eob.cpp (might fix warning about possible null ptr deref)
KYRA: (HOF) - fix possible out of bounds array access
KYRA: (HOF) - fix possible null ptr dereference in sequences_hof.cpp
KYRA: (EOB) - remove dead code in screen_eob.cpp
KYRA: (LOL) - fix possible null ptr dereference in scene_lol.cpp
KYRA: (EOB) - remove unused variable in scene_eob.cpp
KYRA: (LOL) - fix warning about possible out of bounds access in lol.cpp
KYRA: (LOL) - add assert in items_lol.cpp (should silence warning about possible out of bounds access)
KYRA: (LOL) - add comment in gui_lol.cpp
KYRA: (EOB) - fix possible null ptr dereference in gui_eob.cpp
KYRA: (EOB) - silence warning about improper use of negative value in gui_eob.cpp
SWORD25: Silence warning in the Lua code

This fixes warnings like this that crop up when compiling sword25
with Apple clang 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
Merge pull request #319 from fingolfin/lua-warning

SWORD25: Silence warning in the Lua code
WINTERMUTE: Use int32 instead of int in classes.