Refactor for cleanliness

Move files into separate folders for ease of reading, include source
directory so we can use angle bracket includes, adjust build system to
make directories for objects

Makefile

@@ -1,6 +1,7 @@
 CC=gcc
 OUT=oats.out
-LIBS=-I.
+INCLUDES=-I.
+LIBS=
 ARGS=
 
 RELEASE=0
@@ -16,7 +17,7 @@ CFLAGS=$(GFLAGS) $(DFLAGS)
 endif
 
 DIST=build
-SRC:=tag.c memory.c vec.c sv.c lisp.c reader.c eval.c main.c
+SRC:=lib/arena.c lib/vec.c lib/sv.c lisp/tag.c lisp/context.c lisp/lisp.c lisp/reader.c lisp/eval.c main.c
 OBJ:=$(SRC:%.c=$(DIST)/%.o)
 DEPDIR=$(DIST)/dependencies
 DEPS:=$(SRC:%.c=$(DEPDIR)/%.d)
@@ -25,10 +26,10 @@ DEPS:=$(SRC:%.c=$(DEPDIR)/%.d)
 all: $(DIST)/$(OUT)
 
 $(DIST)/%.o: %.c | $(DIST) $(DEPDIR)
-	$(CC) $(CFLAGS) $(DEPFLAGS) $(DEPDIR)/$*.d -c $< -o $@ $(LIBS)
+	$(CC) $(INCLUDES) $(CFLAGS) $(DEPFLAGS) $(DEPDIR)/$*.d -c $< -o $@ $(LIBS)
 
 $(DIST)/$(OUT): $(OBJ) | $(DIST)
-	$(CC) $(CFLAGS) $^ -o $@ $(LIBS)
+	$(CC) $(INCLUDES) $(CFLAGS) $^ -o $@ $(LIBS)
 
 .PHONY: run
 run: $(DIST)/$(OUT)
@@ -38,11 +39,19 @@ run: $(DIST)/$(OUT)
 clean:
 	rm -rfv $(DIST)/*
 
-$(DIST):
+$(DIST): | $(DIST)/lib $(DIST)/lisp
 	mkdir -p $(DIST)
 
+$(DIST)/lib:
+	mkdir -p $(DIST)/lib
+
+$(DIST)/lisp:
+	mkdir -p $(DIST)/lisp
+
 $(DEPDIR):
 	mkdir -p $(DEPDIR)
+	mkdir -p $(DEPDIR)/lib
+	mkdir -p $(DEPDIR)/lisp
 
 .PHONY:
 watch: