Add make-backup-files command for backup toggling, from upstream mailing list:
http://lists.gnu.org/archive/html/qemacs-devel/2004-11/msg00007.html
http://bugs.gentoo.org/75052

--- buffer.c.orig	2009-03-07 21:14:02.000000000 +0100
+++ buffer.c	2009-03-07 21:15:40.000000000 +0100
@@ -1657,12 +1657,14 @@
     if (stat(filename, &st) == 0)
         mode = st.st_mode & 0777;
 
-    /* backup old file if present */
-    if (strlen(filename) < MAX_FILENAME_SIZE - 1) {
+    /* backup old file if present and make-backup-files is on */
+    if(mbf == 1) {
+      if (strlen(filename) < MAX_FILENAME_SIZE - 1) {
         if (snprintf(buf1, sizeof(buf1), "%s~", filename) < ssizeof(buf1)) {
             // should check error code
             rename(filename, buf1);
         }
+      }
     }
 
     /* CG: should pass mode to buffer_save */
--- qe.c.orig	2009-03-07 21:14:09.000000000 +0100
+++ qe.c	2009-03-07 21:17:01.000000000 +0100
@@ -71,6 +71,7 @@
 static int screen_height = 0;
 static int no_init_file;
 static const char *user_option;
+mbf = 1;
 
 /* mode handling */
 
@@ -5316,6 +5317,14 @@
     do_refresh(qs->first_window);
 }
 
+static void make_backup_files(EditState *s) {
+	if(mbf == 1) {
+		mbf = 0;
+	} else {
+		mbf = 1;
+	}
+}
+
 /* compute default path for find/save buffer */
 static void get_default_path(EditState *s, char *buf, int buf_size)
 {
--- qeconfig.h.orig	2009-03-07 21:14:19.000000000 +0100
+++ qeconfig.h	2009-03-07 21:17:37.000000000 +0100
@@ -192,6 +192,7 @@
           "downcase-region", do_changecase_region, ESi, -1, "*v")
     CMD3( KEY_CTRLX(KEY_CTRL('u')), KEY_NONE,
           "upcase-region", do_changecase_region, ESi, 1, "*v")
+    CMD0( KEY_NONE, KEY_NONE, "make-backup-files", make_backup_files)
 
     /*---------------- Command handling ----------------*/
 
--- qe.h.orig	2009-03-07 21:14:26.000000000 +0100
+++ qe.h	2009-03-07 21:17:53.000000000 +0100
@@ -1765,6 +1765,7 @@
 /* image.c */
 void fill_border(EditState *s, int x, int y, int w, int h, int color);
 int qe_bitmap_format_to_pix_fmt(int format);
+int mbf;
 
 /* shell.c */
 EditBuffer *new_shell_buffer(EditBuffer *b0, const char *name,