You could create your own version of the necessary configurations from the existing ones.
First copy the latest XML file from: $MATLABROOT\bin\win64\mexopts\intel_fortran_13_vs2012.xml and place it on the desktop. Next modify it to work with your compiler version. Mostly you'll have to adjust it to look for the IFORT_COMPILER15 environment variable. You might need to modify a few other paths...
Finally when you want to compile a Fortran MEX-file, simply specify your custom config file as:
mex -f intel_fortran_15_vs2013.xml -largeArrayDims some_func.f
If you're interested, here are my versions of the XML files (C, C++, and Fortran): GitHub Gist