2.7 has a new DeprecationWarning inside the build_ext command for code
which sets the 'compiler' to anything other than a string or None.
Because the warning occurs within property getter / setters, it needs
to boost the stacklevel for the warning above the default value of 1.
In addition, the setter is called from within '__setattr__', which means
that it needs to be incremented again in that case.

The attached patch does both of these things.