Lots of hacking to make a very simple "ls" utility.

I added a dead-simple malloc that only allows allocations < 4096 bytes.
It just forwards the request to mmap() every time.

I also added simplified versions of opendir() and readdir().

VirtualFileSystem/FileHandle.h

@@ -12,6 +12,8 @@ public:
     Unix::ssize_t read(byte* buffer, Unix::size_t count);
     int stat(Unix::stat*);
 
+    ssize_t get_dir_entries(byte* buffer, Unix::size_t);
+
     ByteBuffer readEntireFile();
 
 #ifdef SERENITY