Support multiline rules

[Vincas Dargis]

```
$ cat /tmp/test
@{uid}={
[0-9],
[1-9][0-9],
[1-9][0-9][0-9],
[1-9][0-9][0-9][0-9],
[1-9][0-9][0-9][0-9][0-9],
[1-9][0-9][0-9][0-9][0-9][0-9],
[1-9][0-9][0-9][0-9][0-9][0-9][0-9],
[1-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9],
[1-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9],
[1-4][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]
}
$ /usr/sbin/apparmor_parser -qp /tmp/test
@{uid}={

AppArmor parser error for /tmp/test in /tmp/test at line 2: Found unexpected character: '['
```

Multiline rules would increase readability/reviewability in specific cases, though this might be overkill if this feature will need lot's of parser changes.

Or am I doing something wrong here?

[John Johansen (jjohansen)]

Multi-line rule are supported in some places (dbus, signal, etc). However this is dependent on how the rule is parsed.

Variable assignments currently use the newline to indicate the end of the variable. They don't currently parse the variable content, so it is possible to introduce thing like a single opening brace '{' in the variable.

How much we could change this now and remain backwards compatible with the majority of actual policy is unclear atm