This test focuses on ocamldoc "-open" command line option.
It ensures that the modules passed as argument to this "-open" option
are opened in the initial environment of ocamldoc.

More precisely, it checks that

* both cmi files and inner modules can be opened
* modules are opened in the left-to-right order

The test builds a latex documentation file for the three modules
"Main", "Alias" and "Inner". Changes to ocamldoc latex output might
trigger spurious errors in this test.
