Update version and maintainer information

Set version information to 1.1 for the next libsmack release.
Change maintainer email from @intel.com to @linux.intel.com.
Add smack_is_label_valid() function to check correctness of SMACK label

Kernel does not validate the Smack label - instead the label will be
cut on the first incorrect character (after parsing at least one
correct character).
This function gives the user possibility to verify the correctness
of the Smack label before use.