Add makefile and restructure

Makefile

@@ -0,0 +1,27 @@
+
+CC := gcc
+CFLAGS := -ggdb -O0 -std=c99 -Wall -Wextra -Wpedantic
+
+OBJS := obj/arena.o obj/alloc_backend.o
+
+all : test/test_arena
+
+test/test_arena : src/test_arena.c $(OBJS) | test
+	$(CC) -o $@ $(CFLAGS) $^
+
+obj/%.o : src/%.c | obj
+	$(CC) -o $@ -c $(CFLAGS) $<
+
+obj:
+	mkdir -p $@
+
+bin:
+	mkdir -p $@
+
+test:
+	mkdir -p $@
+
+clean:
+	rm -rf obj bin test
+
+.PHONY: clean obj test bin all