alignment information on VarDecls in more cases
This commit improves upon https://reviews.llvm.org/D21099. The code that
computes the source alignment now understands array subscript
expressions, binary operators, derived-to-base casts, and several more
expressions.
rdar://problem/59242343
Differential Revision: https://reviews.llvm.org/D78767
from GCC's in that we warn on *any* increase in alignment requirements, not
just those that are enforced by hardware. Please let us know if this causes
major problems for you (which it shouldn't, since it's an optional warning).
llvm-svn: 110959