scripts: apibuild: parse 'Since' for functions
scripts: apibuild: parse 'Since' for functions

This patch adds 'version' parameter to generated XML API for functions
and functypes.

The 'version' metadata has been added with e0e0bf6628 by parsing .syms
files. This commit does not override that but it will warn if there is
not 'Since' metadata with new additions.

There is not clear benefit for keeping both. For now, I've added a
warning in case there is a mismatch between the version provided by
.syms and docstring.

Signed-off-by: Victor Toso <39b7599ff73bbf5db531748ba5250f21fa7120ff@redhat.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

jfehlig/libvirt,zippy2/libvirt,libvirt/libvirt,olafhering/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt,zippy2/libvirt,olafhering/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,crobinso/libvirt,libvirt/libvirt,libvirt/libvirt,jfehlig/libvirt