provide default value of __SDIR__ in common.h
provide default value of __SDIR__ in common.h

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