pattern/bencode: Various fixes (#393)

* Fix bencode dictionary

When parsing a bencode dictionary, the end character 'e' was never
consumed. This caused a misinterpretation of the character as struct Value of
an unknown type 'e'.

* Fix bencode list

A list was not included in the Value's parsing logic so it may have
been mistakenly parsed as a string.

* Fix std::ctype::isprint not including space

The space character, 0x20, is considered as a printable character in ASCII
and in >=C89. Adding it to the range of std::ctype::isprint also fixes
other std::ctype functions that use it.

* Fix bencode byte string formatting

Byte strings do not render nicely in pattern data's value column if they
contain non-printable characters. This commit makes the value of byte
strings to be surrounded by quotation marks, and renders a warning text
without quotation marks if the byte string contains non-printable
characters.

includes/std/ctype.pat

@@ -85,7 +85,7 @@ namespace auto std::ctype {
         @return True if `c` is part of this range, false otherwise
     */
     fn isprint(char c) {
-        return c >= '0' && c <= '~';
+        return c >= ' ' && c <= '~';
     };
 
     /**