Configure et al: Move the definition of library only flags

We're currently using the attributes 'defines', 'cppflags', 'cflags'
etc quite liberally, with no regard for where that ends up.  Quite a
few of those flags are actually only relevant for the libraries
(mostly libcrypto), so it's safe to say that those could be applied to
the libraries only.

So, we move some of those flags to 'lib_defines', 'lib_cppflags',
'lib_cflags', etc.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5560)