Always include afsconfig.h in autogenerated files

Always include afsconfig.h in autogenerated files

Modify rxgen and compile_et so that the files they output always
contain afsconfig.h before afs/param.h. This avoids problems where
afs/param.h, or headers included from it, rely on having the results
of configure tests available.

Change-Id: I0198500a17abd31ee1057d6780cbe5a5e1bc8c59
Reviewed-on: http://gerrit.openafs.org/1913
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>