Code simplification: Use single macro to detect SWIG.

* subversion/include/svn_types.h
  (SVN_DEPRECATED, SVN_EXPERIMENTAL): Only test SWIG instead of the
    macro for each language.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1543234 13f79535-47bb-0310-9956-ffa450edef68