kmod_module: use 'modname/aliasname' as key for hash

1 alias may correspond to more than 1 module. This would cause a
conflict in the hash table when inserting a module there and bad things
could happen.

Now we use 'modname/aliasname' as key, '/aliasname' part being optional.
Internally kmod_module_new_from_alias() will setup a 'modname/aliasname'
string and pass to kmod_module_new_from_name() that will treat the case
with a '/' in the name.

User might call kmod_module_new_from_name() without any slashes, so the
key my not contain it.
diff --git a/TODO b/TODO
index 3014107..28b4fcd 100644
--- a/TODO
+++ b/TODO
@@ -32,8 +32,5 @@
    - dump configuration
    - use softdep, install and remove commands
 
-Bugs:
+Known Bugs:
 
-* With last changes to the hash of kmod module's, if an alias resolves to more
-  than one module it will conflict in the table. The proper solution is to use
-  'modname/modalias' as the hash key.