autoconf: Combine the x86/solaris configuration stanzas

This reduces some clutter and makes it easier to see what is
different.

Change-Id: I2bad8b085daf04444d2740287c106008e2650bc9
Reviewed-on: http://gerrit.openafs.org/10463
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>