Use span type, rather than stride type for += operand
Fix for dependent types in span
Test if the given reduction operator is defined for the type.
Fix assertion failures caused by signed/unsigned and integer width mismatches in cilk_for
- For example: _Cilk_for (int i = 0; i < 10UL; i++);
- When checking for wraparound in cilk_for, use the same bitwidth for all APSInt values
- Make APSInt signed
Use CapturedStmt to implement SIMD data clauses

- added tests for goto, break and return with simd loops
Ignore implicit casts in cilk_for loop limit and stride
- Mark implicit constructor calls by adding an ImplicitCastExpr node
  as its parent.
- Added new function Expr::GetSubExprAsWritten() that returns the
  first non-implicit subexpression.