merge m17n patch

add libwc

libwc/char_conv.c

@@ -0,0 +1,21 @@
+
+#include "wc.h"
+
+static wc_ces char_conv_f_ces = 0, char_conv_t_ces = WC_CES_WTF;
+static wc_status char_conv_st;
+
+void
+wc_char_conv_init(wc_ces f_ces, wc_ces t_ces)
+{
+    wc_input_init(f_ces, &char_conv_st);
+    char_conv_st.state = -1;
+    char_conv_f_ces = f_ces;
+    char_conv_t_ces = t_ces;
+}
+
+Str
+wc_char_conv(char c)
+{
+    return wc_Str_conv((*char_conv_st.ces_info->char_conv)((wc_uchar)c, &char_conv_st),
+	WC_CES_WTF, char_conv_t_ces);
+}