Fix 'struct plot_info' memory leak

The plot_info was never freed, so every time you'd plot something, we'd
leak memory.

I'm running valgrind to see if there's anything bad going on.  So far it
all looks fairly benign.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

profile.c

@@ -743,4 +743,5 @@ void plot(struct graphics_context *gc, int w, int h, struct dive *dive)
 	cairo_close_path(gc->cr);
 	cairo_stroke(gc->cr);
 
+	free(pi);
 }