The C/C++ standards don't define what time_t is, only that it is
arithmetic (and real for C11, and integral for C++). It should not be
used in portable software and is only used as the return value for some
libc calls.
A common definition for time_t is int64_t, so we'll switch to that
permanently in our own APIs. System APIs will of course stick with
time_t.
* multi_usrp, multi_usrp_clock, and associated classes accessible through C
* Added Doxygen documentation explaining structure and API
* Simple RX and TX streaming examples
* Unit tests for different parts of C interface and C++ error conversion
