definitions as aliases, to be removed in release 3.0.  Also renamed the source
files implementing these two socket types.  This change does not break existing
applications nor bindings, but allows us to fix the documentation and user guide
now, rather than keeping the old (confusing) names.

Removed various exotic -Wxxx flags in the OpenPGM build to get us to what is actually
required and reasonable; added in -fno-strict-aliasing since OpenPGM generates lots
of warnings about dereferencing typed-punned pointers; removed the OpenPGM extra flags
from libzmq_la_CXXFLAGS and left them only in libzmq_la_CFLAGS so that our code
is not built with the OpenPGM extra flags.

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.

C and C++ headers moved from bindings/ to include/, bindings/ removed
--with-c and --with-cpp options to configure removed, C and C++ now built
and installed by default

zmq_encoder/decoder are able to add/trim prefixes from messages; fair queueing and load balancing algorithms factorised into separate classes