Override DEFAULT_DIFF_PROGRAM in diffutils 2.8.1

[Albert Chin]

Patch to add configure option to override DEFAULT_DIFF_PROGRAM. If
diffutils is built with --program-prefix or --program-transform-name,
the default, "diff", won't make much sense. Or maybe we should modify
this to transform the default, "diff", with $(transform)?

-- 
albert chin (address@hidden)

-- snip snip
--- configure.ac.orig   Fri Apr 26 10:51:24 2002
+++ configure.ac        Wed May  8 21:18:16 2002
@@ -43,8 +43,13 @@
 AC_C_INLINE
 AC_C_VARARRAYS
 
-AC_DEFINE(DEFAULT_DIFF_PROGRAM, "diff",
-  [Name of "diff" program, unless overridden.])
+_default_diff_program=diff
+AC_ARG_WITH(default-diff-program,
+  AC_HELP_STRING([--with-default-diff-program=prog],
+  [Name of default diff program (default = diff)]),
+  [_default_diff_program="$withval"])
+AC_DEFINE_UNQUOTED(DEFAULT_DIFF_PROGRAM, "$_default_diff_program",
+  [Name of "diff" program])
 
 AC_DEFINE(DEFAULT_EDITOR_PROGRAM, "ed",
   [Name of editor program, unless overridden.])