The new `BuildFilter()` API can be used by runc/libcontainer to build
a libseccomp filter from the spec. This means that they also do not need
any internal structures any more because we indirectly build it from the
internal `Seccomp` type.
The new `ValidateProfile()` API can be used by higher level consumers,
which want to ensure that a seccomp profile string can be transferred
into a libseccomp filter.
Signed-off-by: Sascha Grunert <sgrunert@suse.com>