fix Object.free (#982)

* lib/std/collections: add HashMap.@each_entry()
* lib/std/json: fix Object.free() when object is a map
* lib/std/collections: fix allocator use in Object.{set,set_at,append}
* lib/std: add char.from_hex
* lib/std/collections: print arrays and objects compactly
* lib/std/io: fix Formatter.vprintf result
* lib/std/io/stream: rename module for ByteBuffer
* lib/std/io/stream: make Scanner a Stream reader
* lib/std/io: make std{in,err,out} return File* if no libc

lib/std/io/stream/limitreader.c3

@@ -1,4 +1,4 @@
-module std::io::stream;
+module std::io;
 
 struct LimitReader
 {