Drop a few unneeded ctor calls (missed code review comment).
[FastISel][AArch64] Extend 'select' lowering to support also i1 to i16.

Related to rdar://problem/18960150.
[FastISel][AArch64] Fold the cmp into the select when possible.

This folds the compare emission into the select emission when possible, so we
can directly use the flags and don't have to emit a separate compare.

Related to rdar://problem/18960150.
[FastISel][AArch64] Optimize select when one of the operands is a 'true' or 'false' value.

Optimize selects of i1 in the presence of 'true' and 'false' operands to simple
logic operations.

This fixes rdar://problem/18960150.