This will allow the variable abstractions to fully encapsulate values while
still permitting binary searches on sorted rows.
* csvm-expand: Renamed from `csvm2csv'. Add directive support.
* csvm2csv: New script to perform sorting. Invokes aforementioned.
* test/test-csvm2csv: Update for sorting.
* build-aux/csvm2csv: Fail on invalid var definition.
(expand_vars): Fail in invalid reference.
(parseline): Fail on non-numeric range.
* build-aux/test/test-csvm2csv
(test-fail-unknown-var-ref, test-fail-non-numeric-range)
(test-fail-invalid-var-dfn): New tests.
This allows variables to contain any type of expansion, treating them
as (recursively) string replacements.
* csvm2csv: Add Copyright year.
(expand_vars): New function.
(parseline): Use it. Expand before all other replacements so that
variable expansions may support all types of expressions. Expand
variables in range expressions.
* test/test-csvm2csv: New file.