[demangler] Avoid alignment warning
[demangler] Avoid alignment warning

The alignment specified by a constant for the field
`BumpPointerAllocator::InitialBuffer` exceeded the alignment
guaranteed by `malloc` and `new` on Windows. This change set
the alignment value to that of `long double`, which is defined
by the used platform.

It fixes https://bugs.llvm.org/show_bug.cgi?id=37944.

Differential Revision: https://reviews.llvm.org/D48889


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@336311 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm