Fix MPFR Flog implementation

Fix MPFR Flog implementation

	* src/ent/floatfns.c (Flog10): Use RETURN_WHEN_INDEF to check
	before dividing by log 10.
	(Flog2): Use RETURN_WHEN_INDEF to check before dividing by log 2.
	(Flog): Properly add parameters to Flog.  Use
	the common RETURN_WHEN_INDEF when Flog return indefinite.
	Plus some whitespace fixes.

Signed-off-by: Nelson Ferreira <nelson.ferreira@ieee.org>