Initial import of filter parser

Current runs as its own program, partially implemented.
Commiting for the sake of sharing access / backup.
Still needs a lot of work.

filter_sandbox/Makefile

@@ -0,0 +1,8 @@
+all:
+	gcc -c tree.c -o tree.o
+	lex zmap.l
+	yacc -d --debug --verbose zmap.y
+	gcc tree.o lex.yy.c y.tab.c -o test
+
+clean:
+	rm *.o a.out test