Characters that should be allowed in a symbol

[Aloso]

*

Common in regular expressions and globs, e.g. foo | grep a.*

Supporting this shouldn't be a problem.

=

Needed e.g. when running cargo --config KEY=VALUE

Supporting this is more difficult, because maps use the syntax { key1=value1, key2=value2 }. An alternative would be to require spaces: { key1 = value1, key2 = value2 } or accept = in symbols except when parsing the key of an object.