Set inhibit-compacting-font-caches to t by default on MS-Windows

* src/font.c (syms_of_font) [WINDOWSNT]: Set
inhibit-compacting-font-caches to t by default.

* etc/NEWS: Mention the change.

etc/NEWS

@@ -2663,6 +2663,11 @@ is being used, except in Far Eastern locales.  When this variable is
 non-zero, Emacs at startup sets 'locale-coding-system' to the
 corresponding encoding, instead of using 'w32-ansi-code-page'.
 
+---
+** The default value of 'inhibit-compacting-font-caches' is t on MS-Windows.
+Experience shows that compacting font caches causes more trouble on
+MS-Windows than it helps.
+
 +++
 ** On NS the behaviour of drag and drop can now be modified by use of
 modifier keys in line with Apples guidelines.  This makes the drag and

src/font.c

@@ -5509,7 +5509,14 @@ and cannot switch to a smaller font for those characters, set
 this variable non-nil.
 Disabling compaction of font caches might enlarge the Emacs memory
 footprint in sessions that use lots of different fonts.  */);
+
+#ifdef WINDOWSNT
+  /* Compacting font caches causes slow redisplay on Windows with many
+     large fonts, so we disable it by default.  */
+  inhibit_compacting_font_caches = 1;
+#else
   inhibit_compacting_font_caches = 0;
+#endif
 
   DEFVAR_BOOL ("xft-ignore-color-fonts",
 	       Vxft_ignore_color_fonts,