Remove two uses of the gcc specific 'aligned' attribute. This

Remove two uses of the gcc specific 'aligned' attribute.  This
is partly because this attribute caused trouble in the past (the
SmallVector one had to be changed from aligned to aligned(8) due
to causing crashes on i386 for example; in theory the same might
be needed in the Allocator case...).  But it's mostly because
there seems to be no point in special casing gcc here.  Using the
same implementation for all compilers results in better testing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115462 91177308-0d34-0410-b5e6-96231b3b80d8