lineedit: first shot at optional unicode bidi input support

function                                             old     new   delta
read_line_input                                     4886    5003    +117
in_uint16_table                                        -      97     +97
in_interval_table                                      -      78     +78
static.rtl_b                                           -      68     +68
unicode_isrtl                                          -      55     +55
isrtl_str                                              -      51     +51
static.rtl_p                                           -      42     +42
unicode_conv_to_printable2                           633     477    -156
------------------------------------------------------------------------------
(add/remove: 6/0 grow/shrink: 1/1 up/down: 508/-156)          Total: 352 bytes

Signed-off-by: Tomas Heinrich <heinrich.tomas@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/Config.in b/Config.in
index e7bb05d..e0c01f3 100644
--- a/Config.in
+++ b/Config.in
@@ -196,6 +196,14 @@
 	  With this option off, any Unicode char with width > 1
 	  is substituted on output.
 
+config UNICODE_BIDI_SUPPORT
+	bool "Bidirectional character-aware line input"
+	default y
+	depends on FEATURE_ASSUME_UNICODE && !LOCALE_SUPPORT
+	help
+	  With this option on, right-to-left Unicode characters
+	  are treated differently on input (e.g. cursor movement).
+
 config LONG_OPTS
 	bool "Support for --long-options"
 	default y