number of application threads to use 0MQ sockets is unlimited; app_threads parameter in zmq_init is unused and obsolete

This lets us build the binaries in a portable fashion w/o having to worry
about how to link with the C++ runtime.

Compiling C++ code with -D_POSIX_SOURCE on Solaris is unsupported, so remove it.
Isolate GCC-isms inside checks that we are actually using GCC/G++.
Only check for -lstdc++ when on GCC and doing static linking.

Removed README.source, TODO.source since these are irrelevant to a generic
git package.
Fixed spelling in debian/copyright.
Removed RFC check in debian/rules, again irrelevant to a generic git package.