- Correct PyBool_FromLong's return type and its description.

- Unify function description mode ("Return X" vs "Returns X")

CVS: ----------------------------------------------------------------------
CVS: Enter Log.  Lines beginning with `CVS:' are removed automatically
CVS:
CVS: Committing in .
CVS:
CVS: Modified Files:
CVS: 	Doc/api/concrete.tex
CVS: ----------------------------------------------------------------------