trim tracker urls and renamed isprint to is_print

src/escape_string.cpp

@@ -87,11 +87,16 @@ namespace libtorrent
 		return c >= '0' && c <= '9';
 	}
 
-	bool isprint(char c)
+	bool is_print(char c)
 	{
 		return c >= 32 && c < 127;
 	}
 
+	bool is_space(char c)
+	{
+		return c == ' ' || c == '\t';
+	}
+
 	char to_lower(char c)
 	{
 		return (c >= 'A' && c <= 'Z') ? c - 'A' + 'a' : c;