CallExpr::getFirstExpr() Fix a cut/paste error surfaced by Elliot
Merge pull request #962 from noakesmichael/Elliot-0

CallExpr::getFirstExpr() Fix simple "cut/paste" error

This implementation of getFirstExpr() had an, effectively, cut/paste error.  This was not surfaced by
existing tests but was picked up by some new work Elliot is doing.



compiled: STD clang/darwin, STD gcc/linux64
tested: paratest
review: none