There is a bug in the Wolfram Symbolic Transfer Protocol Development in C (Windows).
I described it in the next answer by myself, from which I summarize:
One cannot successfully compile the
C:\Program Files\Wolfram Research\Mathematica\10.0\SystemFiles\Links\WSTP\DeveloperKit\Windows\WSTPExamples\addtwo, even if one follows the instructions in "WSTP Development in C (Windows)" strictly.
Question: Does anybody have a patch?
Well, I have one and I can post it here as an answer if somebody gives me a hint on how to do it.
BTW, is anybody interested in Mathematica related programming with DELPHI, I have done a bit of code porting, any suggestions on pascal style porting are welcomed.