Ensure i686-nacl long long is aligned 8 bytes (like malign-double)

Set NaCl OSTargetInfo to have LongLongAlign = 64. Otherwise, it will
pick up the setting of 32 from X86_32TargetInfo.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199335 91177308-0d34-0410-b5e6-96231b3b80d8