Experimental #saveoptions command

Add a #saveoptions extended command, to allow saving configuration
settings from within the game. This is still highly experimental,
and gives plenty of warnings before asking to overwrite the file.

Lack of option saving is one of the biggest complaints new players
have, so this should help with it.  More experienced players with
highly customized config file should not use this feature, as it
completely rewrites the file, removing all comments and non-config
lines.

src/symbols.c

@@ -5,6 +5,9 @@
 #include "hack.h"
 #include "tcap.h"
 
+static void savedsym_add(const char *, const char *, int);
+static struct _savedsym *savedsym_find(const char *, int);
+
 extern const uchar def_r_oc_syms[MAXOCLASSES];      /* drawing.c */
 
 #if defined(TERMLIB) || defined(CURSES_GRAPHICS)
@@ -661,6 +664,74 @@ free_symsets(void)
     /* assert( symset_list == NULL ); */
 }
 
+struct _savedsym {
+    char *name;
+    char *val;
+    int which_set;
+    struct _savedsym *next;
+};
+struct _savedsym *saved_symbols = NULL;
+
+void
+savedsym_free(void)
+{
+    struct _savedsym *tmp = saved_symbols, *tmp2;
+
+    while (tmp) {
+        tmp2 = tmp->next;
+        free(tmp->name);
+        free(tmp->val);
+        free(tmp);
+        tmp = tmp2;
+    }
+}
+
+static struct _savedsym *
+savedsym_find(const char *name, int which_set)
+{
+    struct _savedsym *tmp = saved_symbols;
+
+    while (tmp) {
+        if (which_set == tmp->which_set && !strcmp(name, tmp->name))
+            return tmp;
+        tmp = tmp->next;
+    }
+    return NULL;
+}
+
+static void
+savedsym_add(const char *name, const char *val, int which_set)
+{
+    struct _savedsym *tmp = NULL;
+
+    if ((tmp = savedsym_find(name, which_set)) != 0) {
+        free(tmp->val);
+        tmp->val = dupstr(val);
+    } else {
+        tmp = (struct _savedsym *)alloc(sizeof(struct _savedsym));
+        tmp->name = dupstr(name);
+        tmp->val = dupstr(val);
+        tmp->which_set = which_set;
+        tmp->next = saved_symbols;
+        saved_symbols = tmp;
+    }
+}
+
+void
+savedsym_strbuf(strbuf_t *sbuf)
+{
+    struct _savedsym *tmp = saved_symbols;
+    char buf[BUFSZ];
+
+    while (tmp) {
+        Sprintf(buf, "%sSYMBOLS=%s:%s\n",
+                (tmp->which_set == ROGUESET) ? "ROGUE" : "",
+                tmp->name, tmp->val);
+        strbuf_append(sbuf, buf);
+        tmp = tmp->next;
+    }
+}
+
 /* Parse the value of a SYMBOLS line from a config file */
 boolean
 parsesymbols(register char *opts, int which_set)
@@ -720,6 +791,7 @@ parsesymbols(register char *opts, int which_set)
             }
         }
     }
+    savedsym_add(opts, strval, which_set);
     return TRUE;
 }