pager: honour internal aliases

If paging is configured for a command all it's internal defined aliases
will be paged as well. This will make attend=log cause 'hg history'
to run the pager. However custom aliases will not be paged by default.

--HG--
branch : stable
help: minor tweak to push help

--HG--
branch : stable
tests: move generaldelta test to inline python (issue4064)

--HG--
branch : stable