some build fixes for compile issues reported

src/allmain.c

@@ -854,7 +854,6 @@ const char *opts;
 {
     char *op;
     boolean negated = FALSE;
-    boolean retval = TRUE;
 
     while ((op = index(opts, ',')) != 0) {
         *op++ = 0;

src/mapglyph.c

@@ -247,7 +247,7 @@ int glyph;
     return encbuf;
 }
 
-char *
+const char *
 decode_mixed(buf, str)
 char *buf;
 const char *str;