[CodeGen] Fix assignments of inline layouts into the byref structure

[CodeGen] Fix assignments of inline layouts into the byref structure

When using blocks, a byref structure is created to represent the
closure. The "byref.layout" field of this structure is an i8*. However,
some 'inline' layouts are represented as i64's, not i8*'s.

Prior to r246985 we cast the i64 'inline' layout to an i8* before
assigning it into the byref structure. This patch brings the cast back
and adds a regression test.

rdar://23713871

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@256185 91177308-0d34-0410-b5e6-96231b3b80d8