Stop lying about pointers' required alignments.

Stop lying about pointers' required alignments.

These extra specializations were added in the depths of history (r67984 from
2009) and are clearly problematic now. The pointers actually are aligned to the
default (8 bytes), since otherwise UBsan would be complaining loudly.

I *think* it originally made sense because there was no "alignof" to infer the
correct value so the generic case went with what malloc returned (8-byte
aliged objects), and on 32-bit machines this specialization was correct. It
became wrong when we started compiling for 64-bit, and caused a UBSan failure
when we tried to put a ValueHandle into a DenseMap.

Should fix the Green Dragon UBSan bot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289496 91177308-0d34-0410-b5e6-96231b3b80d8