Bundle a copy of xmlrpc++ (CVS as of 20101026) to use as an easier to build
(than libxmlrpc-c3) client on win32, and also as a server in the near future.
Upstream version modified as follows:
* Added numerous required includes
* Fixed some sprintf format strings
* Added support for the nil type
* Included <config.h> in all .cpp files
* Enable dynamic linking for pthreads-win32
* Add -mthreads to compiler and linker flags
* Modify nsis installer script to include pthreadGC2.dll and mingwm10.dll
The win32 installer is generated by running scripts/mknsisinst.sh via
`make nsisinst'. This target is available only if `makensis' is present
on the build system.