message: Add `-Wextra` and `-Wpedantic` warning flags
diff: @@ -10,7 +10,7 @@ NAS2DLIBDIR := $(NAS2DDIR)lib/
  NAS2DLIB := $(NAS2DLIBDIR)libnas2d.a
  CPPFLAGS := $(CPPFLAGS_EXTRA)
  -CXXFLAGS_WARN := -Wall -Wno-unknown-pragmas -Wnull-dereference -Wcast-qual -Wcast-align -Wshadow -Wnon-virtual-dtor -Woverloaded-virtual -Wmissing-include-dirs -Winvalid-pch -Wmissing-format-attribute $(WARN_EXTRA)
  +CXXFLAGS_WARN := -Wall -Wextra -Wpedantic -Wno-unknown-pragmas -Wnull-dereference -Wcast-qual -Wcast-align -Wshadow -Wnon-virtual-dtor -Woverloaded-virtual -Wmissing-include-dirs -Winvalid-pch -Wmissing-format-attribute $(WARN_EXTRA)
  CXXFLAGS := $(CXXFLAGS_EXTRA) -std=c++17 $(CXXFLAGS_WARN) -I$(NAS2DINCLUDEDIR) $(shell sdl2-config --cflags)
  LDFLAGS := $(LDFLAGS_EXTRA) -L$(NAS2DLIBDIR) $(shell sdl2-config --libs)
  LDLIBS := $(LDLIBS_EXTRA) -lnas2d -lSDL2 -lSDL2_image -lSDL2_mixer -lSDL2_ttf -lphysfs -lGL -lGLEW
  