Fix alignment of unwind data.

Fix alignment of unwind data.

For alignment purposes, the instruction array will always have an even
number of entries, with the final entry potentially unused (in which
case the array will be one longer than indicated by the count of unwind
codes field).

Reviewed by Charles Davis and Nico Rieck.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185760 91177308-0d34-0410-b5e6-96231b3b80d8