Add an explict list of exported symbols with just the functions
declared in the public headers, and use __{BEGIN,END}_HIDDEN_DECLS
in the internal headers to optimize internal functions

ok jsing@

tags as requested by miod and tedu

Stop pulling pqueue.h into ssl_locl.h since only a small part of libssl
actually needs it. Instead, just include it in the files where it is
actually necessary.

Also remove standard includes from pqueue.h so that they are not available
as a side effect. Just add the two includes that are needed to pqueue.c.

ok miod@

Move the `pqueue' part of libcrypto, which is a glorified sorted linked list
of 64-bit data, and only used by DTLS, to libssl where it belongs.

Remove pqueue_print() which is a debugging interface and serves no useful
purpose, except for the regress test, which grows its own pqueue_print()
routine.

Bump libcrypto major and libssl minor.

WARNING: do not update your tree right now, more changes are coming, which
will ride the libcrypto major bump.