Include special handling of WhileStmt in deadBlockElimination
Drop use of WhileStmt::replaceChild
Merge pull request #980 from noakesmichael/whileChild

WhileStmt::replaceChild    Remove

There was one location in deadBlockElimination that was relying on WhileStmt::replaceChild to
NULL-out the condition expression.

1) Converted that in to an operation that removes the entire WhileStmt, this is what we really want.

2) Dropped the implementation of WhileStmt::replaceChild

Compiled: STD clang/darwin, STD gcc/linux64, LLVM gcc/linux64
Tested: paratest --verify
Review: none