Compile test-core in C++

[Chenxiong Qi]

Hi,

I've converted QofCollection to a C++ class. A side-effect is that I
have to make src/test-core be able to compile in C++. I'm an absolute
newbie to autotools, still not get a workable solution so far after
doing some research on this. Could you give some guide how to
accomplish this conversion. Conversion only involves the compiler
changed to a C++ compiler, and the file's extension changed to cpp if
necessary. Nothing else if src/test-core/* are compiled in C++ without
errors.

BTW, besides the conversion to C++ class, I will write unit tests to
ensure new QofCollection class works as expected.

Thanks!

Regards,
Chenxiong Qi