telnet: add telnet history support

adapted from Yoshinori Sato's patch:
2f07f4600a

Change-Id: I084b86d316b0aa6e9593f007c024961dbda805e9
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1310
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

src/helper/configuration.h

@@ -40,5 +40,6 @@ int configuration_output_handler(struct command_context *cmd_ctx,
 FILE *open_file_from_path(const char *file, const char *mode);
 
 char *find_file(const char *name);
+char *get_home_dir(const char *append_path);
 
 #endif	/* CONFIGURATION_H */