Extracted bash-specific test

Signed-off-by: Oleg Bulatov <oleg@bulatov.me>
Add Lexeme::QQString

Signed-off-by: Oleg Bulatov <oleg@bulatov.me>
Add LineConcat to QQString

Signed-off-by: Oleg Bulatov <oleg@bulatov.me>
Add Lexeme::Escaped
One more example

Signed-off-by: Oleg Bulatov <oleg@bulatov.me>