units buffer.
(math-build-units-table): Add entries to the units table to be used
to display the values in the units buffer.
(math-build-units-table-buffer): Use the display entry of the units
table when non nil.
(calc-define-unit): Add an option to enter display value of unit.
possible.
(math-unit-prefixes): Replace floats with powers of ten.
(math-standard-units-systems): Replace floats with integers.
(math-make-unit-string): Remove extra spaces in output.
(math-get-default-units,math-put-default-units): New functions.
(math-default-units-table): New variable.
(calc-convert-units, calc-convert-temperature): Add machinery to
supply default values.
(calc-num-units, calc-den-units): New variables.
(calc-explain-units, calc-explain-units-rec): Replace variables
num-units and den-units by declared variables.
(math-cu-unit-list): New variable.
(math-build-units-table, math-compare-unit-names)
(math-convert-units, math-convert-units-rec): Replace variable
unit-list by declared variable.
(math-fbu-base, math-fbu-entry): New variables.
(math-find-base-units, math-find-base-units-rec): Replace variables
base and entry by declared variables.
(math-which-standard): New variable.
(math-to-standard-units, math-to-standard-rec): Replace variable
which-standard by declared variable.
(math-fcu-u): New variable.
(math-find-compatible-unit, math-find-compatible-unit-rec):
Replace variable u by declared variable.
(math-cu-new-units, math-cu-pure): New variables.
(math-convert-units, math-convert-units-rec): Replace variables
new-units and pure by declared variables.
(math-try-cancel-units): New variable.
(math-simplify-units-quotient): Replace variable try-cancel-units by
declared variable.
Replaced argument expr in all calls of math-defsimplify by
math-simplify-expr.
(math-simplify-units-prod): Replaced variable expr by declared
variable math-simplify-expr.
Change all toplevel `setq' forms to `defvar' forms, and move them
before their first use. Use `when', `unless'. Remove trailing
periods from error forms. Add description and headers suggested by
Emacs Lisp coding conventions.
