Introduce WhileStmt::blockInfoGet/Set to trap attempts to invoke this virtual function on a WhileStmt
Guard against effort to invoke blockInfoGet/Set on a WhileStmt
Merge pull request #930 from noakesmichael/while-1

Remove calls to blockInfoGet/Set via a pointer to a WhileStmt

1) Introduced WhileStmt::blockInfoGet/Set that complain if they are called
2) Redirected all internal uses of WhileStmt::blockInfoGet/Set to the BlockStmt version
3) Tracked down remaining external calls to blockInfoGet/Set for WhileStmt

Compiled: STD clangdarwin, STD gcc/linux64, LLVM gcc/linux64
Tested: paratest and paratest --verify --llvm
Review: none