This reworks the code to be more strict about accepting stream specifiers. From
now on we strictly enforce the syntax in the documentation up until the
decisive part of the stream specifier. Therefore matching stream specifiers
always need to be correct, non matching specifiers only need to be correct
until the decisive part.

Also recursion is changed to a simple loop.
Signed-off-by: Marton Balint <cus@passwd.hu>