added Drop trait to allow more automated memory management

src/drop.h

@@ -0,0 +1,22 @@
+#ifndef _fencer_drop_h
+#define _fencer_drop_h
+
+typedef struct {
+    void (*const drop)(void* self);
+} IDrop;
+
+typedef struct {
+    void const* data;
+    IDrop const* tc;
+} Drop;
+
+#define impl_Drop_for(T, drop_f)\
+static inline Drop T##_as_Drop(T* x) {\
+    TC_FN_TYPECHECK(void, drop_f, T*);\
+    static IDrop const tc = {\
+        .drop = (void(*const)(void*)) drop_f,\
+    };\
+    return (Drop){.tc = &tc, .data = x};\
+}
+
+#endif // !_fencer_drop_h