Converted all ASCII tabs to ASCII spaces using a 8 character
tab stop, for all files, except for all Makefiles (plus rpm.mk).
The `git diff -w` reports no changes.
Add new logn(x, n [,eps]) builtin to compute logarithms to base n.
Verify that eps arguments (error tolerance arguments that override
the default epsilon value) to builtin functions have proper values.
Previously the eps argument had little to no value checks for
many builtin functions.
Document in help files for builtin functions that take eps arguments,
the LIMIT range for such eps values.
Updated CHANGES.
Updated help/unexpected.
Added help files for d2g(), d2r(), g2d(), g2r(), r2d(), r2g().
Added regression test code for the same functions.
Fixed a few minor typos.
