Add support for endian-specific reference outputs.
 - Use naming convention such as ".reference_output.big-endian" or, for type
   specific outputs, something like ".reference_output.big-endian.small".

git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@180647 91177308-0d34-0410-b5e6-96231b3b80d8
[tests] Fix automative-bitcount test for big-endian LP64 systems.

git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@180648 91177308-0d34-0410-b5e6-96231b3b80d8
[tests] Add big-endian specific reference outputs for some tests.
 - The outputs themselves are taken from Hal's PPC64 runs.

 - I only added outputs for tests where I verified that the code was not
   endian-portable, and where the tests did real work unrelated to that
   importability. There are other tests (like the bitfield ones, and the cast
   ones) which are not endian-portable but where the nature of the test is tied
   to the exact memory layout. Those tests I feel should be rewritten to be
   endian agnostic.

git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@180649 91177308-0d34-0410-b5e6-96231b3b80d8