add initial log() implementation.
some cleanups and corrections for error estimates. start of log testing.
Merge branch 'master' into add-log

Resolved Conflicts:
	Makefile
	Makefile.icc
	fastermath.h
	fm_internal.h
	tester.c
more cleanups
remove obsolete files
fix comments
add empty files for logarithms
include debug info
add some code for log2()