Use equally-sized buttons in wxMSW horizontal toolbars

Only use TBSTYLE_AUTOSIZE, adjusting each button to the size it really needs,
for the toolbars with wxTB_HORZ_LAYOUT style as they don't have any uniform
button size anyhow.

(cherry picked from commit 967bdbf994)

src/msw/toolbar.cpp

@@ -1091,11 +1091,12 @@ bool wxToolBar::Realize()
 
                 // Instead of using fixed widths for all buttons, size them
                 // automatically according to the size of their bitmap and text
-                // label, if present. This particularly matters for toolbars
-                // with the wxTB_HORZ_LAYOUT style: they look hideously ugly
-                // without autosizing when the labels have even slightly
-                // different lengths.
-                button.fsStyle |= TBSTYLE_AUTOSIZE;
+                // label, if present. They look hideously ugly without autosizing
+                // when the labels have even slightly different lengths.
+                if ( HasFlag(wxTB_HORZ_LAYOUT) )
+                {
+                    button.fsStyle |= TBSTYLE_AUTOSIZE;
+                }
 
                 bitmapId++;
                 break;