Remove the deprecated single-alignment IRBuilder API for memcpy/memmove (NFC)

Summary:
This change is part of step six in the series of changes to remove the alignment
argument from memcpy/memmove/memset in favour of alignment attributes. At this
point all users of the IRBuilder APIs for creating a memcpy/memmove call given
a single value for alignment have been updated. We want to discourage usage of
these old APIs in favour of the newer ones that allow for separate source and
destination alignments, so this patch deletes the old API.

Specifically, we remove from IRBuilder:
CallInst *CreateMemCpy(Value *Dst, Value *Src, uint64_t Size, unsigned Align,
                       bool isVolatile = false, MDNode *TBAATag = nullptr,
                       MDNode *TBAAStructTag = nullptr,
                       MDNode *ScopeTag = nullptr,
                       MDNode *NoAliasTag = nullptr)
CallInst *CreateMemCpy(Value *Dst, Value *Src, Value *Size, unsigned Align,
                       bool isVolatile = false, MDNode *TBAATag = nullptr,
                       MDNode *TBAAStructTag = nullptr,
                       MDNode *ScopeTag = nullptr,
                       MDNode *NoAliasTag = nullptr)
CallInst *CreateMemMove(Value *Dst, Value *Src, uint64_t Size, unsigned Align,
                        bool isVolatile = false, MDNode *TBAATag = nullptr,
                        MDNode *ScopeTag = nullptr,
                        MDNode *NoAliasTag = nullptr)
CallInst *CreateMemMove(Value *Dst, Value *Src, Value *Size, unsigned Align,
                        bool isVolatile = false, MDNode *TBAATag = nullptr,
                        MDNode *ScopeTag = nullptr,
                        MDNode *NoAliasTag = nullptr)

Steps:
Step 1) Remove alignment parameter and create alignment parameter attributes for
memcpy/memmove/memset. ( rL322965, rC322964, rL322963 )
Step 2) Expand the IRBuilder API to allow creation of memcpy/memmove with differing
source and dest alignments. ( rL323597 )
Step 3) Update Clang to use the new IRBuilder API. ( rC323617 )
Step 4) Update Polly to use the new IRBuilder API. ( rL323618 )
Step 5) Update LLVM passes that create memcpy/memmove calls to use the new IRBuilder API,
and those that use use MemIntrinsicInst::[get|set]Alignment() to use [get|set]DestAlignment()
and [get|set]SourceAlignment() instead. ( rL323886, rL323891, rL324148, rL324273, rL324278,
rL324384, rL324395, rL324402, rL324626, rL324642, rL324653, rL324654, rL324773, rL324774,
rL324781, rL324784, rL324955, rL324960, rL325816, rL327398, rL327421, rL328097 )
Step 6) Remove the single-alignment IRBuilder API for memcpy/memmove, and the
MemIntrinsicInst::[get|set]Alignment() methods.

Reference
   http://lists.llvm.org/pipermail/llvm-dev/2015-August/089384.html
   http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html

llvm-svn: 328317