comctl32: Constify some variables (3 of 8)

[Andrew Talbot]

Changelog:
    comctl32: Constify some variables.

diff -urN a/dlls/comctl32/theme_combo.c b/dlls/comctl32/theme_combo.c
--- a/dlls/comctl32/theme_combo.c	2006-10-25 20:00:59.000000000 +0100
+++ b/dlls/comctl32/theme_combo.c	2007-03-31 20:07:35.000000000 +0100
@@ -45,7 +45,7 @@
 #define EDIT_CONTROL_PADDING   1
 
 /* paint text of combobox, needed for read-only drop downs. */
-static void paint_text (HWND hwnd, HDC hdc, DWORD dwStyle, COMBOBOXINFO* cbi)
+static void paint_text (HWND hwnd, HDC hdc, DWORD dwStyle, const COMBOBOXINFO *cbi)
 {
     INT  id, size = 0;
     LPWSTR pText = NULL;