[ScheduleDAGInstrs::buildSchedGraph()] Handling of memory dependecies rewritten.

Recommited, after some fixing with test cases.

Updated test cases:
test/CodeGen/AArch64/arm64-misched-memdep-bug.ll
test/CodeGen/AArch64/tailcall_misched_graph.ll

Temporarily disabled test cases:
test/CodeGen/AMDGPU/split-vector-memoperand-offsets.ll
test/CodeGen/PowerPC/ppc64-fastcc.ll (partially updated)
test/CodeGen/PowerPC/vsx-fma-m.ll
test/CodeGen/PowerPC/vsx-fma-sp.ll

http://reviews.llvm.org/D8705
Reviewers: Hal Finkel, Andy Trick.

llvm-svn: 259673