Added freelist header

ya_freelist.h

@@ -0,0 +1,39 @@
+/*
+ * Yet Another Malloc
+ * ya_freelist.h
+ */
+
+#ifndef YA_FREELIST_H
+#define YA_FREELIST_H
+
+/*----------*/
+/* Includes */
+/*----------*/
+
+#include <stdint.h> // for intptr_t
+
+/*------------*/
+/* Data types */
+/*------------*/
+
+struct fl {
+    intptr_t *block;
+    struct fl *prev;
+    struct fl *next;
+};
+
+/*--------------*/
+/* Declarations */
+/*--------------*/
+
+struct fl *fl_find(intptr_t min_size);
+
+void fl_split(struct fl *fl);
+
+void fl_join_prev(struct fl *fl);
+
+void fl_join_next(struct fl *fl);
+
+void fl_join(struct fl *fl);
+
+#endif