update-alternatives.bbclass: Refactor the implementation
Refactor in order to:
* Deprecate the old interfaces, but keep them for compatibility
* Provide a new, interface -- capable of working with split packages
* Each update-alternative will now set proper "per-file" provides
Note: this adds a warning message when the older deprecated behavior is
used. The older behavior has been fully tested using oe-core.
Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
