package.bbclass: add getter of additional metadata
Two variables are searched for value of additional package metadata:
* PACKAGE_ADD_METADATA_<PKGTYPE>
* PACKAGE_ADD_METADATA
First found variable with defined value wins.
<PKGTYPE> is a parameter of getter and expected to be a distinct name
of specific package type. For example: 'DEB' or 'RPM'.
Variable can contain multiple [one-line] metadata fields, separated by
literal sequence '\n'. Separator can be redefined through variable flag
'separator'. Getter returns found value with separator replaced with
newline character.
As side-effect, searched variables acquired flags 'type' (equals to
'list') and 'separator'.
Signed-off-by: Leonid Borisenko <ive.found@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
