This test used to take more than 10min because an instance of valgrind
was launched for each separate equivalence check.  The list of
equivalences to checks are not given in a file, and only two valgrind
instances are run.  The test takes less than 15sec.

* src/ltltest/equalsf.cc: New file.
* src/ltltest/Makefile.am (reduccmp, reductaustr): Build using
equalsf.cc.
* src/ltltest/reduccmp.test: Rewrite.
* src/ltltest/uwrm.test: Also rewrite, and use valgrind.