autoconf: add test for typedef'd structs

autoconf: add test for typedef'd structs

AC_CHECK_LINUX_STRUCT does not work for structs which are typedef'd.
The gcc will complain with "error: storage size of ‘_test’ isn’t known"
and fail the test.
Thus the new test-macro AC_CHECK_LINUX_TYPED_STRUCT.

Change-Id: Ib3e933c4e09a3e950ca8d8e7a66909d86f10cfdf
Reviewed-on: http://gerrit.openafs.org/4718
Reviewed-by: Christof Hanke <christof.hanke@rzg.mpg.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>