cython: update Clean.run() to remove cython-generated files
cython: update Clean.run() to remove cython-generated files

rc/sfepy,sfepy/sfepy,RexFuzzle/sfepy,RexFuzzle/sfepy,sfepy/sfepy,RexFuzzle/sfepy,vlukes/sfepy,vlukes/sfepy,sfepy/sfepy,vlukes/sfepy,RexFuzzle/sfepy,lokik/sfepy,BubuLK/sfepy,rc/sfepy,lokik/sfepy,BubuLK/sfepy,rc/sfepy,lokik/sfepy,BubuLK/sfepy,lokik/sfepy