Export only functions that are part of the API

By default, all functions are exported in a shared library. Use a linker
version script to keep only the API-related functions in the dynamic
symbols list.

Plus, this allows symbol versioning, i.e. unlimited API compatibility.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Add the version script to library dependencies

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Support for VMCOREINFO

Provide API to get the content VMCOREINFO.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Support for VMCOREINFO_XEN

Provide API to get the content VMCOREINFO_XEN.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>