hush: export -n support

function                                             old     new   delta
builtin_export                                       206     256     +50
set_local_var                                        248     265     +17
expand_variables                                    2204    2203      -1

diff --git a/shell/Config.in b/shell/Config.in
index 6cc11ce..57969f0 100644
--- a/shell/Config.in
+++ b/shell/Config.in
@@ -232,6 +232,13 @@
 	help
 	  Enable support for shell functions in hush. +800 bytes.
 
+config HUSH_EXPORT_N
+	bool "Support export '-n' option"
+	default n
+	depends on HUSH
+	help
+	  Enable support for export '-n' option in hush. It is a bash extension.
+
 config LASH
 	bool "lash (deprecated: aliased to hush)"
 	default n