compiler fixes

The compiler flag -s is not necessary and causes build failure on some
systems (macOS, clang compilers) due to it being deprecated.
Additionally, on those same systems, tools/aif2pcm/main.c failed to
compile due to an overly cautious compiler not liking some struct
declarations.
These changes afaik do not affect other builds.

tools/mid2agb/Makefile

@@ -1,6 +1,6 @@
 CXX := g++
 
-CXXFLAGS := -std=c++11 -O2 -s -Wall -Wno-switch -Werror
+CXXFLAGS := -std=c++11 -O2 -Wall -Wno-switch -Werror
 
 SRCS := agb.cpp error.cpp main.cpp midi.cpp tables.cpp