Add includes for <boost/foreach.hpp>. Resolves PR #5.

[warnes]

Resolves errors about missing definition for BOOST_FOREACH described in PR #5:

make -j14
[  5%] Built target doxygen_target
Scanning dependencies of target gnuradio-osmosdr
[ 20%] Built target pygen_apps_99d5b
[ 25%] Built target pygen_python_4b7cb
[ 28%] Built target pygen_apps_2f344
[ 28%] Built target osmosdr_grc_yaml_blocks
[ 34%] Building CXX object lib/CMakeFiles/gnuradio-osmosdr.dir/source_impl.cc.o
[ 34%] Building CXX object lib/CMakeFiles/gnuradio-osmosdr.dir/sink_impl.cc.o
/media/psf/inoui/src/gr-osmosdr/lib/sink_impl.cc: In constructor ‘sink_impl::sink_impl(const string&)’:
/media/psf/inoui/src/gr-osmosdr/lib/sink_impl.cc:250:29: error: expected primary-expression before ‘*’ token
  250 |   BOOST_FOREACH( sink_iface *dev, _devs )
      |                             ^
/media/psf/inoui/src/gr-osmosdr/lib/sink_impl.cc:250:30: error: ‘dev’ was not declared in this scope; did you mean ‘div’?
  250 |   BOOST_FOREACH( sink_iface *dev, _devs )
      |                              ^~~
      |                              div
/media/psf/inoui/src/gr-osmosdr/lib/sink_impl.cc:250:3: error: ‘BOOST_FOREACH’ was not declared in this scope; did you mean ‘BOOST_CATCH’?
  250 |   BOOST_FOREACH( sink_iface *dev, _devs )
      |   ^~~~~~~~~~~~~
      |   BOOST_CATCH
/media/psf/inoui/src/gr-osmosdr/lib/sink_impl.cc:251:31: error: ‘dev_chan’ was not declared in this scope
  251 |     for (size_t dev_chan = 0; dev_chan < dev->get_num_channels(); dev_chan++) {
      |                               ^~~~~~~~
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc: In constructor ‘source_impl::source_impl(const string&)’:
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc:198:32: error: expected primary-expression before ‘arg’
  198 |      BOOST_FOREACH(std::string arg, arg_list) {
      |                                ^~~
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc:198:6: error: ‘BOOST_FOREACH’ was not declared in this scope; did you mean ‘BOOST_CATCH’?
  198 |      BOOST_FOREACH(std::string arg, arg_list) {
      |      ^~~~~~~~~~~~~
      |      BOOST_CATCH
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc:424:31: error: expected primary-expression before ‘*’ token
  424 |   BOOST_FOREACH( source_iface *dev, _devs )
      |                               ^
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc:424:32: error: ‘dev’ was not declared in this scope; did you mean ‘div’?
  424 |   BOOST_FOREACH( source_iface *dev, _devs )
      |                                ^~~
      |                                div
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc:424:3: error: ‘BOOST_FOREACH’ was not declared in this scope; did you mean ‘BOOST_CATCH’?
  424 |   BOOST_FOREACH( source_iface *dev, _devs )
      |   ^~~~~~~~~~~~~
      |   BOOST_CATCH
/media/psf/inoui/src/gr-osmosdr/lib/source_impl.cc:425:31: error: ‘dev_chan’ was not declared in this scope
  425 |     for (size_t dev_chan = 0; dev_chan < dev->get_num_channels(); dev_chan++) {
      |                               ^~~~~~~~
make[2]: *** [lib/CMakeFiles/gnuradio-osmosdr.dir/build.make:76: lib/CMakeFiles/gnuradio-osmosdr.dir/sink_impl.cc.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: *** [lib/CMakeFiles/gnuradio-osmosdr.dir/build.make:63: lib/CMakeFiles/gnuradio-osmosdr.dir/source_impl.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:375: lib/CMakeFiles/gnuradio-osmosdr.dir/all] Error 2
make: *** [Makefile:141: all] Error 2