added 3.6 sse4-i16x8 compfails to fail_db

Added to fail_db.txt all 4616 entries on sse4-i16x8 compfails. Failes first appeared in LLVM 3.6 after commit 214628 (Chandler). Tracker: http://llvm.org/bugs/show_bug.cgi?id=20540.