[balsa/stop-using-gtkbuttonbox] libbalsa_button_box_button: Document a difference

[Peter Bloomfield <peterb src gnome org>]

commit 662449b51bd357c020688b4b2e14935638c578f2
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Sat Aug 29 15:10:24 2020 -0400

    libbalsa_button_box_button: Document a difference
    
    The spacing is not always the same as with a GtkButtonBox.
    
    modified:   libbalsa/misc.c

 libbalsa/misc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/libbalsa/misc.c b/libbalsa/misc.c
index ae143d4e7..170b9dd35 100644
--- a/libbalsa/misc.c
+++ b/libbalsa/misc.c
@@ -1261,8 +1261,8 @@ libbalsa_parser_options(void)
  *
  * markup:     mnemonic text for the button;
  * size_group: managed by the caller, to make buttons the same size;
-               could be created as gtk_size_group_new(GTK_SIZE_GROUP_BOTH),
-               to ensure common widths and heights;
+ *             could be created as gtk_size_group_new(GTK_SIZE_GROUP_BOTH),
+ *             to ensure common widths and heights;
  * align:      how to align the button in its allocated space.
  *
  * To replace a GtkButtonBox with the default GTK_BUTTONBOX_EDGE style,
@@ -1272,6 +1272,9 @@ libbalsa_parser_options(void)
  * align should be GTK_ALIGN_CENTER for all buttons;
  * To replace a GtkButtonBox with style GTK_BUTTONBOX_EXPAND,
  * align should be GTK_ALIGN_FILL for all buttons.
+ *
+ * In the EDGE case with more than two buttons, and in the SPREAD case,
+ * the spacing is not identical to GtkButtonBox's.
  */
 
 /* Margin to increase the width of the button, to approximate the look