; Avoid compilation warnings under -Og

* src/w32.c (w32_read_registry):
* src/font.c (font_parse_fcname):
* src/fns.c (Fnconc):
* src/editfns.c (tzlookup):
* src/frame.c (x_set_frame_parameters): Avoid compiler warnings
about maybe-uninitialized variables.

src/editfns.c

@@ -174,7 +174,7 @@ tzlookup (Lisp_Object zone, bool settz)
       else if (plain_integer || (CONSP (zone) && FIXNUMP (XCAR (zone))
 				 && CONSP (XCDR (zone))))
 	{
-	  Lisp_Object abbr;
+	  Lisp_Object abbr = Qnil;
 	  if (!plain_integer)
 	    {
 	      abbr = XCAR (XCDR (zone));

src/fns.c

@@ -2522,7 +2522,7 @@ usage: (nconc &rest LISTS)  */)
 
       CHECK_CONS (tem);
 
-      Lisp_Object tail;
+      Lisp_Object tail = Qnil;
       FOR_EACH_TAIL (tem)
 	tail = tem;
 

src/font.c

@@ -1468,7 +1468,7 @@ font_parse_fcname (char *name, ptrdiff_t len, Lisp_Object font)
 	      else
 		{
 		  /* KEY=VAL pairs  */
-		  Lisp_Object key;
+		  Lisp_Object key = Qnil;
 		  int prop;
 
 		  if (q - p == 10 && memcmp (p + 1, "pixelsize", 9) == 0)

src/frame.c

@@ -3798,7 +3798,7 @@ x_set_frame_parameters (struct frame *f, Lisp_Object alist)
   Lisp_Object icon_left, icon_top;
 
   /* And with this.  */
-  Lisp_Object fullscreen;
+  Lisp_Object fullscreen = Qnil;
   bool fullscreen_change = false;
 
   /* Record in these vectors all the parms specified.  */

src/w32.c

@@ -9358,7 +9358,7 @@ w32_read_registry (HKEY rootkey, Lisp_Object lkey, Lisp_Object lname)
   DWORD vsize, vtype;
   LPBYTE pvalue;
   Lisp_Object val, retval;
-  const char *key, *value_name;
+  const char *key, *value_name = NULL;
   /* The following sizes are according to size limitations
      documented in MSDN.  */
   wchar_t key_w[255+1];