config.def.h: typo in comment.

config.def.h

@@ -1,7 +1,7 @@
 
 #define FONT "-*-*-medium-r-*-*-*-120-75-75-*-70-*-*"
 #define BOLDFONT "-*-*-bold-r-*-*-*-120-75-75-*-70-*-*"
-/* If italic is not availbel, fall back to bold. */
+/* If italic is not available, fall back to bold. */
 #define ITALICFONT "-*-*-medium-o-*-*-*-120-75-75-*-70-*-*," BOLDFONT
 #define ITALICBOLDFONT "-*-*-bold-o-*-*-*-120-75-75-*-70-*-*," BOLDFONT