Fix issue with endless allocation loop

Shrinking columns wasn't updating hidden rows in the storage buffer on
resizing. When growing the columns again, this resulted in an endless
allocation loop.

Only one real change was made here, and that was `raw.iter_mut()` to
`raw.iter_mut_raw()`. The method `shrink_cols` was relocated to be
adjacent to `grow_cols` in the code.

src/grid/mod.rs

@@ -252,6 +252,14 @@ impl<T: Copy + Clone> Grid<T> {
         self.cols = cols;
     }
 
+    fn shrink_cols(&mut self, cols: index::Column) {
+        for row in self.raw.iter_mut_raw() {
+            row.shrink(cols);
+        }
+
+        self.cols = cols;
+    }
+
     /// Remove lines from the visible area
     ///
     /// The behavior in Terminal.app and iTerm.app is to keep the cursor at the
@@ -437,14 +445,6 @@ impl<T> Grid<T> {
     // pub fn swap_lines(&mut self, src: index::Line, dst: index::Line) {
     //     self.raw.swap(*src, *dst);
     // }
-
-    fn shrink_cols(&mut self, cols: index::Column) {
-        for row in self.raw.iter_mut() {
-            row.shrink(cols);
-        }
-
-        self.cols = cols;
-    }
 }
 
 impl<'a, T> Iterator for GridIterator<'a, T> {