Fenced code blocks lose leading indentation and get an empty language

When parsing a fenced code block in markdown/1.2:

• the content is trimmed, so the indentation of the first line (and trailing whitespace) is lost;
• when no language is specified, the code macro gets an empty language parameter instead of none;
• the whole info string is used as the language (e.g. java title instead of java).

Steps to reproduce

Parse:

```
    indented
x
```

Result

onMacroStandalone [code] [language=] [indented
x]

Expected

onMacroStandalone [code] [language=none] [    indented
x]