Implement the Nakagami statistical distribution as an extension.

libstdc++-v3/ChangeLog

libstdc++-v3/include/ext/random

libstdc++-v3/include/ext/random.tcc

...estsuite/ext/random/nakagami_distribution/cons/default.cc

.../testsuite/ext/random/nakagami_distribution/cons/parms.cc

...suite/ext/random/nakagami_distribution/operators/equal.cc

...ite/ext/random/nakagami_distribution/operators/inequal.cc

...e/ext/random/nakagami_distribution/operators/serialize.cc

...ami_distribution/requirements/explicit_instantiation/1.cc

...ext/random/nakagami_distribution/requirements/typedefs.cc