Prevent array index out of bounds for symbol

Bug-Debian: https://github.com/tats/w3m/issues/38

display.c

@@ -1129,18 +1129,18 @@ addChar(char c, Lineprop mode)
 	    }
 #ifdef USE_M17N
 	    if (w == 2 && WcOption.use_wide)
-		addstr(graph2_symbol[(int)c]);
+		addstr(graph2_symbol[(unsigned char)c % N_GRAPH_SYMBOL]);
 	    else
 #endif
-		addch(*graph_symbol[(int)c]);
+		addch(*graph_symbol[(unsigned char)c % N_GRAPH_SYMBOL]);
 	}
 	else {
 #ifdef USE_M17N
 	    symbol = get_symbol(DisplayCharset, &w);
-	    addstr(symbol[(int)c]);
+	    addstr(symbol[(unsigned char)c % N_SYMBOL]);
 #else
 	    symbol = get_symbol();
-	    addch(*symbol[(int)c]);
+	    addch(*symbol[(unsigned char)c % N_SYMBOL]);
 #endif
 	}
     }

file.c

@@ -7611,7 +7611,7 @@ conv_symbol(Line *l)
 		symbol = get_symbol(DisplayCharset, &w);
 #endif
 	    }
-	    Strcat_charp(tmp, symbol[(int)c]);
+	    Strcat_charp(tmp, symbol[(unsigned char)c % N_SYMBOL]);
 #ifdef USE_M17N
 	    p += len - 1;
 	    pr += len - 1;

fm.h

@@ -1109,6 +1109,7 @@ extern char *graph2_symbol[];
 extern int symbol_width;
 extern int symbol_width0;
 #define N_GRAPH_SYMBOL 32
+#define N_SYMBOL (N_GRAPH_SYMBOL + 14)
 #define SYMBOL_BASE 0x20
 global int no_rc_dir init(FALSE);
 global char *rc_dir init(NULL);

symbol.c

@@ -176,10 +176,10 @@ push_symbol(Str str, char symbol, int width, int n)
 
 #ifdef USE_M17N
     if (width == 2)
-	p = alt2_symbol[(int)symbol];
+	p = alt2_symbol[(unsigned char)symbol % N_SYMBOL];
     else
 #endif
-	p = alt_symbol[(int)symbol];
+	p = alt_symbol[(unsigned char)symbol % N_SYMBOL];
     for (i = 0; i < 2 && *p; i++, p++)
 	buf[i] = (*p == ' ') ? NBSP_CODE : *p;