Make nil and t parse to symbols and make the top level env look them up

src/env.c

@@ -136,6 +136,13 @@ Ast_Node* lookup_symbol(Symbol* sym, Environment* env) {
             return result;
     }
 
+    if (string_equal(sym->identifier, "nil")) {
+        return create_ast_node_nil();
+    }
+    if (string_equal(sym->identifier, "t")) {
+        return create_ast_node_t();
+    }
+
     result = create_ast_node_built_in_function(sym->identifier);
     if (result)
         return result;

src/parse.c

@@ -101,13 +101,6 @@ Ast_Node* parse_keyword(char* text, int* index_in_text) {
 Ast_Node* parse_symbol(char* text, int* index_in_text) {
     // we are now at the first char of the symbol
     char* str_symbol = read_atom(text, index_in_text);
-
-    if (string_equal(str_symbol, "nil")) {
-        return create_ast_node_nil();
-    }
-    if (string_equal(str_symbol, "t")) {
-        return create_ast_node_t();
-    }
     return create_ast_node_symbol(str_symbol);
 }