fix: made is_frame_free(int frame) public

kernel/mem/frame.h

@@ -31,16 +31,17 @@ extern void frame_init(uint_t RAM_in_KB);
 // The frame's content is always zeroed.
 extern void *frame_alloc(void);
 
+extern bool is_frame_free(int frame);
+
 // Free a frame.
 // REMARK: doesn't check whether the frame was previously allocated or not.
 extern void frame_free(void *frame_addr);
 
 // Returns the total number of free frames.
-// This can typically be used by a syscall to retrieve the amount of free RAM.
+// This can typically be used by a syscall to retrieve the amount of free
+// RAM.
 extern uint_t frame_total_free(void);
 
 extern void dbg_frame_allocator(struct terminal_t *term);
 
-extern void dbg_frame_bmp(struct terminal_t *term);
-
 #endif