libevent: use C++ to check for signature of gethostbyname_r
libevent: use C++ to check for signature of gethostbyname_r

C++ by definition requires matching prototype (both number of arguments,
order of arguments, and type of arguments) to be compilable.

Use this property to check for signature of gethostbyname_r(3) at
compile time in order to support cross compiling.

CauldronDevelopmentLLC/cbang,CauldronDevelopmentLLC/cbang,CauldronDevelopmentLLC/cbang,CauldronDevelopmentLLC/cbang