[xmlsec] Problems with C/C++ compilers

[Roumen Petrov]

Aleksey Sanin wrote:
> This is one of several compile-time defines that are used to configure 
> xmlsec. You should use pkg-config, etc. to ensure you use correct flags.

Hmm, other system use header files - see for instance 
openssl/opensslconf.h, libxml/xmlversion.h or etc.
(bad example - pyconfig.h).

So some of flags has to be moved to headers.

Roumen