enable -lcrypto -lssl with all test programs directly.

This removes the need to specify each one individually.

ok doug@
use the correct HOST_OS for the Windows build

ok doug@
Improve and simplify function and header detection logic.

Simplify autoconf checks by using AC_CHECK_FUNCS/HEADERS.
Clarify some ambiguous dependencies around strnlen/strndup.
Unconditionally enable pidwraptest for all arc4random implementations.
Remove HAVE_VASPRINTF conditional, since asprintf requires vasprintf.

ok @doug
wrap arc4random header

ok @doug
Add an OpenSSL compatible ./config wrapper

This allows sofware expecting OpenSSL's config script, to a limited
extent, to continue building without changes.

Thanks to technion for pointing this out and providing the initial
patch.