Added complete call-seq documentation for directory operations across
both mrblib/dir.rb (7 Ruby methods) and src/dir.c (12 C methods):
## Ruby Methods (mrblib/dir.rb):
- Dir instance methods: each, each_child for directory iteration with
enumerator support when no block given
- Dir class methods: entries, children for getting directory contents
as arrays, foreach for iteration, open for directory access with
optional block handling, chdir for changing working directory with
optional block for temporary changes
## C Methods (src/dir.c):
- Dir class methods: delete for removing directories, exist? for checking
directory existence, getwd/pwd for current directory, mkdir for creating
directories with optional permissions, chroot for changing filesystem root,
empty? for checking if directory is empty
- Dir instance methods: new for creating directory objects, close for
closing directory streams, read for reading directory entries, rewind
for repositioning to beginning, seek/tell/pos for directory positioning
Co-authored-by: Atlassian Rovo Dev
Instead of allocating `MAXPATHLEN` buffer string at the beginning,
allocate smaller (64 bytes) buffer, then resize it if needed. The
allocating max size is safe but consumes more memory.
Since `IOError` is a standard exception class in Ruby, there is no need to assume different superclasses.
The Ruby specification allows repeated class definitions as long as the superclass is the same.
This also avoids using the `mruby/ext/io.h` file to reference `E_IO_ERROR`.
Yukihiro "Matz" Matsumoto