patch 8.2.4368: Amiga: a few compiler warnings

Problem:    Amiga: a few compiler warnings.
Solution:   Adjust #ifdefs. Add "UNUSED". (Ola Söder, closes #9756,
            closes #9757)
diff --git a/src/term.c b/src/term.c
index 45dde3c..824f912 100644
--- a/src/term.c
+++ b/src/term.c
@@ -37,7 +37,7 @@
  * A few linux systems define outfuntype in termcap.h to be used as the third
  * argument for tputs().
  */
-# ifdef VMS
+# if defined(VMS) || defined(AMIGA)
 #  define TPUTSFUNCAST (void (*)(unsigned int))
 # else
 #  ifdef HAVE_OUTFUNTYPE