In the `Ranges(...)` generation code a "control" vector which stores
the current index for each range passed to `Ranges`. Previously this vector
was incorrectly initialized to the size of the subranges not the number
of subranges.
Additionally this patch suppresses unused warnings generated by
`stream_init_anchor`.
VC 2013 injects valid when assigning an initializer list to std::set.
This attempts to work around this issue by using std::set's constructors
instead of the assignment operators.
* Support multiple ranges in the benchmark
google-benchmark library allows to provide up to two ranges to the
benchmark method (range_x and range_y). However, in many cases it's not
sufficient. The patch introduces multi-range features, so user can easily
define multiple ranges by passing a vector of integers, and access values
through the method range(i).
* Remove redundant API
Functions State::range_x() and State::range_y() have been removed. They should
be replaced by State::range(0) and State::range(1).
Functions Benchmark::ArgPair() and Benchmark::RangePair() have been removed.
They should be replaced by Benchmark::Args() and Benchmark::Ranges().
