GiNaC/ginac clifford.cpp clifford.h color.h

[Christian Bauer]

Update of /home/cvs/GiNaC/ginac

Modified Files:
	clifford.cpp clifford.h color.h 
Log Message:
- dirac_trace() takes an optional third argument: the expression to use for
  the trace of the unit matrix
- more conventional factor I in gamma5