implement word deletion via ^W

src/toxic_strings.h

@@ -49,6 +49,11 @@ void reset_buf(ChatContext *ctx);
    Return 0 on success, -1 if yank buffer is empty or too long */
 int yank_buf(ChatContext *ctx);
 
+/* Deletes all characters from line starting at pos and going backwards 
+   until we find a space or run out of characters.
+   Return 0 on success, -1 if no line or already at the beginning */
+int del_word_buf(ChatContext *ctx);
+
 /* Removes trailing spaces from line. */
 void rm_trailing_spaces_buf(ChatContext *ctx);