default names for output files are inconsistent

[KrisThielemans]

For a module called swigexample

swig -matlab example.i

generates example_wrap.cxx, a folder +swigexample, and m files calling swigexampleMEX.

This means that either you have to use mex example_wrap.cxx -output swigexampleMEX, or use swig -mexname example_wrap or use swig -o swigexampleMEX.cxx