Centralise generation of the control sequences for arrow keys into a

function in terminal.c, and replace the cloned-and-hacked handling
code in all our front ends with calls to that.

This was intended for code cleanliness, but a side effect is to make
the GTK arrow-key handling support disabling of application cursor
key mode in the Features panel. Previously that checkbox was
accidentally ignored, and nobody seems to have noticed before!

[originally from svn r8896]

putty.h

@@ -854,6 +854,8 @@ char *term_get_ttymode(Terminal *term, const char *mode);
 int term_get_userpass_input(Terminal *term, prompts_t *p,
 			    unsigned char *in, int inlen);
 
+int format_arrow_key(char *buf, Terminal *term, int xkey, int ctrl);
+
 /*
  * Exports from logging.c.
  */