tentative fix for issue #1026 - Enhanced1

Issue reported by ostrosablin (and mentioned previously but I still
I haven't remembered where):  loading a roguesymset removes any utf8
data that has been set up for primary symset.  The curses interface
explicitly initializes roguesymset to the default set and if config
file has specified OPTIONS=symset:Enhanced1 (or some other uft8 set
if someone adds such), that stays the active set but no longer gets
rendered with the intended symbols.

I have no idea whether having symset and roguesymset both use uft8
with different symbols and/or colors works at all and if so whether
it will still work after this revision, but this prevents loading one
set with non-utf8 while the other still uses utf8 from clearing out
the cached utf8 data.

Closes #1026

src/symbols.c

@@ -321,6 +321,11 @@ update_rogue_symset(const struct symparse* symp, int val)
 void
 clear_symsetentry(int which_set, boolean name_too)
 {
+#ifdef ENHANCED_SYMBOLS
+    int other_set = (which_set == PRIMARYSET) ? ROGUESET : PRIMARYSET;
+    enum symset_handling_types old_handling = gs.symset[which_set].handling;
+#endif
+
     if (gs.symset[which_set].desc)
         free((genericptr_t) gs.symset[which_set].desc);
     gs.symset[which_set].desc = (char *) 0;
@@ -337,7 +342,10 @@ clear_symsetentry(int which_set, boolean name_too)
         gs.symset[which_set].name = (char *) 0;
     }
 #ifdef ENHANCED_SYMBOLS
-    free_all_glyphmap_u();
+    /* if 'which_set' was using UTF8, it isn't anymore; if the other set
+       isn't using UTF8, discard the data for that */
+    if (old_handling == H_UTF8 && gs.symset[other_set].handling != H_UTF8)
+        free_all_glyphmap_u();
     purge_custom_entries(which_set);
 #endif
 }