Giant const-correctness patch of doom!

Having found a lot of unfixed constness issues in recent development,
I thought perhaps it was time to get proactive, so I compiled the
whole codebase with -Wwrite-strings. That turned up a huge load of
const problems, which I've fixed in this commit: the Unix build now
goes cleanly through with -Wwrite-strings, and the Windows build is as
close as I could get it (there are some lingering issues due to
occasional Windows API functions like AcquireCredentialsHandle not
having the right constness).

Notable fallout beyond the purely mechanical changing of types:
 - the stuff saved by cmdline_save_param() is now explicitly
   dupstr()ed, and freed in cmdline_run_saved.
 - I couldn't make both string arguments to cmdline_process_param()
   const, because it intentionally writes to one of them in the case
   where it's the argument to -pw (in the vain hope of being at least
   slightly friendly to 'ps'), so elsewhere I had to temporarily
   dupstr() something for the sake of passing it to that function
 - I had to invent a silly parallel version of const_cmp() so I could
   pass const string literals in to lookup functions.
 - stripslashes() in pscp.c and psftp.c has the annoying strchr nature

1 files changed, 2 insertions, 2 deletions

diff --git a/ldisc.c b/ldisc.c
index 0e864874..320a9360 100644
--- a/ldisc.c
+++ b/ldisc.c
@@ -22,7 +22,7 @@
                       (ldisc->back->ldisc(ldisc->backhandle, LD_EDIT) || \
 			   term_ldisc(ldisc->term, LD_EDIT))))
 
-static void c_write(Ldisc ldisc, char *buf, int len)
+static void c_write(Ldisc ldisc, const char *buf, int len)
 {
     from_backend(ldisc->frontend, 0, buf, len);
 }
@@ -134,7 +134,7 @@ void ldisc_echoedit_update(void *handle)
     frontend_echoedit_update(ldisc->frontend, ECHOING, EDITING);
 }
 
-void ldisc_send(void *handle, char *buf, int len, int interactive)
+void ldisc_send(void *handle, const char *buf, int len, int interactive)
 {
     Ldisc ldisc = (Ldisc) handle;
     int keyflag = 0;