benchmark

Negative ranges #762 (#787)

* Add FIXME in multiple_ranges_test.cc

* Improve handling of large bounds in AddRange.

Due to breaking the loop too early, AddRange
would miss a final multplier of 'mult' that
was within the numeric range of T.

* Enable negative values for Range argument

Fixes #762.

* Try to fix build of benchmark_gtest

* Try some more to fix build

* Attempt to fix format macros

* Attempt to resolve format errors for mingw32

* Review feedback

Put unit tests in benchmark::internal namespace

Fix error reporting in multiple_ranges_test.cc