Build documentation in make html target

To keep the distchecks for the documentation, the documentation has to
be built in the check target instead of distcheck-hook.

While at it, rename doc/.build to doc/_build. This naming is the
default with sphinx 0.6.2.

doc/conf.py

@@ -69,7 +69,7 @@ release = '1.1.1+'
 
 # List of directories, relative to source directory, that shouldn't be searched
 # for source files.
-exclude_trees = ['.build']
+exclude_trees = ['_build']
 
 # The reST default role (used for this markup: `text`) to use for all documents.
 #default_role = None