benchmark

Print the executable name as part of the context. (#534)

* Print the executable name as part of the context.

A common use case of the library is to run two different
versions of a benchmark to compare them. In my experience
this often means compiling a benchmark twice, renaming
one of the executables, and then running the executables
back-to-back. In this case the name of the executable
is important contextually information.  Unfortunately the
benchmark does not report this information.

This patch adds the executable name to the context reported
by the benchmark.

* attempt to fix tests on Windows

* attempt to fix tests on Windows