feat: recursively walk symlinks pointing at dirs

Before:

```
/tmp/test-recursive-dir-symlinks
├── dir
│  └── test.txt
└── symlinkdir -> /tmp/test-recursive-dir-symlinks/dir
```

After:

```
/tmp/test-recursive-dir-symlinks
├── dir
│  └── test.txt
└── symlinkdir -> /tmp/test-recursive-dir-symlinks/dir
   └── test.txt
```

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

src/main.rs

@@ -366,7 +366,7 @@ impl<'args> Exa<'args> {
                     let mut child_dirs = Vec::new();
                     for child_dir in children
                         .iter()
-                        .filter(|f| f.is_directory() && !f.is_all_all)
+                        .filter(|f| f.points_to_directory() && !f.is_all_all)
                     {
                         match child_dir.to_dir() {
                             Ok(d) => child_dirs.push(d),

src/output/details.rs

@@ -292,7 +292,7 @@ impl<'a> Render<'a> {
 
                 let mut dir = None;
                 if let Some(r) = self.recurse {
-                    if file.is_directory() && r.tree && !r.is_too_deep(depth.0) {
+                    if file.points_to_directory() && r.tree && !r.is_too_deep(depth.0) {
                         trace!("matching on to_dir");
                         match file.to_dir() {
                             Ok(d) => {