blockfreq: Use getSuccessorIndex()

No functionality change.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206082 91177308-0d34-0410-b5e6-96231b3b80d8
blockfreq: Rename BlockFrequencyImpl to BlockFrequencyInfoImpl

This is a shared implementation class for BlockFrequencyInfo and
MachineBlockFrequencyInfo, not for BlockFrequency, a related (but
distinct) class.

No functionality change.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206083 91177308-0d34-0410-b5e6-96231b3b80d8
blockfreq: Remove unnecessary template parameters

Moves redundant template parameters into an implementation detail of
BlockFrequencyInfoImpl.

No functionality change.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206084 91177308-0d34-0410-b5e6-96231b3b80d8
blockfreq: Rename BlockProbInfoT to BranchProbabilityInfoT

No functionality change.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206085 91177308-0d34-0410-b5e6-96231b3b80d8
blockfreq: Document BlockFrequencyInfo terminology

Documents terminology used in the forthcoming rewrite of
BlockFrequencyInfo.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206086 91177308-0d34-0410-b5e6-96231b3b80d8