Remove unprotected global state from EVP_PBE

Remove unprotected global state from EVP_PBE

Nobody adds a custom password-based encryption algorithm, be it a PRF or
one that can be an outermost AlgorithmIdentifier in CMS or its precursors.
This makes the undocumented and unused EVP_PBE_alg_add{,_type}() always
fail. They will be removed in the next major bump.

Thus, we no longer need to maintain a global stack of PBE algorithms that
one thread can happily modify while another one searches it.

In subsequent steps we can then remove another rather pointless use of
OBJ_bsearch_(). "Let's optimize the lookup in a table with two dozen
entries using about as many glorious layers of obfuscating macros."

ok jsing