Mesa: update to Mesa-9.1.5

Signed-off-by: Stephan Raue <stephan@openelec.tv>
scripts: fix some STAMP filenames

Signed-off-by: Stephan Raue <stephan@openelec.tv>
Mesa: convert to new package format

Signed-off-by: Stephan Raue <stephan@openelec.tv>