Include afsconfig.h before anything else

Include afsconfig.h before anything else

afsconfig.h can define various preprocessor symbols that can affect
how system headers behave. For example, the presence of the
_POSIX_PTHREAD_SEMANTICS symbol changes the number of arguments to
getpwnam_r on at least Solaris 8. So, we must include afsconfig.h
before including anything else, to ensure consistency.

Change-Id: I84bc73b3fada5dbc68cd355c24f2f746f2e982b3
Reviewed-on: http://gerrit.openafs.org/6387
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>