Remove sk_find_ex()

This API intends to find the closest match to the needle. M2Crypto
exposes it because it can. This will be fixed by patching the port.

ok jsing

upstream hidden file #include_next workaround for MS C compilers

ok beck@, tb@

Hide symbols in libcrypto/stack

Automated change from the first attempts at the semi automated
Guentherizer 2000.

ok jsing@ tb@ joshua@