libbladeRF: Moved tests out of libbladeRF/ directory

Because the libbladeRF tests were nested under the libbladeRF build,
they were being built with the include paths, library paths,
etc.  used when building libbladeRF.

This was masking build issues that libbladeRF users might experience,
such as MS Visual Studio 12 and earlier failing due to a lack of a
stdbool.h header. (We now include our stdbool.h, and have an option to
disable our C99 compat includes.)

Therefore, these tests have been moved in the build hierarchy to avoid
cross-pollination of the libbladeRF build environment and the tests'
build environment. This should better represent users building against
libbladeRF, and hopefully bring issues to light earlier.
libbladeRF: Do not include <stdbool.h> for C++ code in API header

This is unneccessary and causes build issues when building C++ programs
in Visual Studio 2012 and earlier.
libbladeRF: Added C++ build test

This program is just intended to ensure C++ using libbladeRF build.