DEVEL15-kill-ubik-pthread-env-20080718

DEVEL15-kill-ubik-pthread-env-20080718

LICENSE BSD

Everywhere AFS_PTHREAD_ENV was defined, UBIK_PTHREAD_ENV was defined as
well, so don't make them separate.  Building pthreaded Ubik is controlled
by deciding whether to build the t* versions of various directories, not
by the preprocessor directives.  AFS_PTHREAD_ENV is only defined when
building in those directories.

This change eliminates UBIK_PTHREAD_ENV and uses AFS_PTHREAD_ENV to mean
the same thing.

As a side effect, fixes compiles on arm with --enable-pthreaded-ubik, since
arm never defined UBIK_PTHREAD_ENV.

(cherry picked from commit 9682d4c1073846b13ae0825c8d6b020e5b31559c)