Clang Warnings

[PeterParker]

Slack message from Steven Hahn:

Some of your code in Refs http://trac.mantidproject.org/mantid/ticket/5308 (https://github.com/mantidproject/mantid/commit/9c4606692a4d4f60cc3fb2cb9bc591fb23837bf3) is generating warning in osx with the clang compiler. Would you please rework the following lines?

/Users/svh/Documents/MantidProject/mantid/Code/Mantid/MantidQt/CustomInterfaces/src/CalcCorr.cpp:292:5: warning: ignoring return value of function declared with warn_unused_result attribute [-Wunused-result]
   runPythonCode(pyInput).trimmed();
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
[1005/1462] Building CXX object Mantid...s/CustomInterfaces.dir/src/Elwin.cpp.o
/Users/svh/Documents/MantidProject/mantid/Code/Mantid/MantidQt/CustomInterfaces/src/Elwin.cpp:122:5: warning: ignoring return value of function declared with warn_unused_result attribute [-Wunused-result]
   runPythonCode(pyInput).trimmed();
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
[1010/1462] Building CXX object Mantid.../CustomInterfaces.dir/src/MSDFit.cpp.o
/Users/svh/Documents/MantidProject/mantid/Code/Mantid/MantidQt/CustomInterfaces/src/MSDFit.cpp:86:5: warning: ignoring return value of function declared with warn_unused_result attribute [-Wunused-result]
   runPythonCode(pyInput).trimmed();
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.

[PeterParker]

This issue was originally trac ticket 10527