Terminal browser: swap minibuffer prompts for p and P.

In a trace buffer, 'p' prompts for a pc value, and jumps to the
next (later in time) occasion when that pc is visited. The capital
version, 'P', does the same thing except that it jumps earlier in
time.

Unfortunately, their minibuffer prompts are back to front. 'p' was
prompting "Go to previous visit to PC: ", and 'P' said "next", which
is the opposite of what each one really does.

I think it's all consistent now. The actual behaviour, the F10 help,
and the minibuffer prompts all point in the same direction.

browser/curses.cpp

@@ -1062,7 +1062,7 @@ class TraceBuffer : public Window {
             return true;
         } else if (c == 'p' || c == 'P') {
             screen->minibuf_ask(
-                (c == 'p' ?
+                (c == 'P' ?
                  _("Go to previous visit to PC: ") :
                  _("Go to next visit to PC: ")), this);
             minibuf_reqtype = c;