llvm2.8: Import from meta-java

* llvm is generic enough to be useful outside meta-java
  e.g. we need it to enable llvmpipe galium driver in mesa

* imported without any modification (except indentation), all
  credits go to Henning Heinold and Khem Raj for maintaining
  it in meta-java

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>