Revert r1543234.  SWIG is defined only during the code generation.  The
generated files have SWIGPERL et al defined but not SWIG.  Sorry for
the pointless code-churn.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1543235 13f79535-47bb-0310-9956-ffa450edef68