setup.py: better detection of swig binary
setup.py: better detection of swig binary

BLLIP/bllip-parser,BLLIP/bllip-parser,BLLIP/bllip-parser,BLLIP/bllip-parser,BLLIP/bllip-parser,BLLIP/bllip-parser,BLLIP/bllip-parser,BLLIP/bllip-parser