apply --whitespace: configuration option.

The new configuration option apply.whitespace can take one of
"warn", "error", "error-all", or "strip".  When git-apply is run
to apply the patch to the index, they are used as the default
value if there is no command line --whitespace option.

Andrew can now tell people who feed him git trees to update to
this version and say:

	git repo-config apply.whitespace error

Signed-off-by: Junio C Hamano <junkio@cox.net>

environment.c

@@ -17,6 +17,7 @@ int only_use_symrefs = 0;
 int repository_format_version = 0;
 char git_commit_encoding[MAX_ENCODING_LENGTH] = "utf-8";
 int shared_repository = 0;
+const char *apply_default_whitespace = NULL;
 
 static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir,
 	*git_graft_file;