Use Automake 1.11's parallel-tests feature.

* configure.ac: Enable parallel-tests.
* src/eltltest/defs.in, src/evtgbatest/defs.in,
src/ltltest/defs.in, src/tgbatest/defs.in: Always output verbose
tests.  Make a subdirectory for each test case.
* src/ltltest/Makefile.am, src/eltltest/Makefile.am,
src/tgbatest/Makefile.am, src/evtgbatest/Makefile.am: Remove
CLEANFILES and clean the test subdirectories in a distclean-local
rule instead.
* src/eltltest/acc.test, src/eltltest/nfa.test,
src/evtgbatest/explicit.test, src/evtgbatest/ltl2evtgba.test,
src/evtgbatest/product.test, src/evtgbatest/readsave.test,
src/ltltest/equals.test, src/ltltest/lunabbrev.test,
src/ltltest/nenoform.test, src/ltltest/parse.test,
src/ltltest/parseerr.test, src/ltltest/reduc.test,
src/ltltest/reduccmp.test, src/ltltest/syntimpl.test,
src/ltltest/tostring.test, src/ltltest/tunabbrev.test,
src/ltltest/tunenoform.test, src/tgbatest/bddprod.test,
src/tgbatest/complementation.test, src/tgbatest/dfs.test,
src/tgbatest/dupexp.test, src/tgbatest/eltl2tgba.test,
src/tgbatest/emptchk.test, src/tgbatest/emptchke.test,
src/tgbatest/emptchkr.test, src/tgbatest/explicit.test,
src/tgbatest/explpro2.test, src/tgbatest/explpro3.test,
src/tgbatest/explpro4.test, src/tgbatest/explprod.test,
src/tgbatest/ltl2neverclaim.test, src/tgbatest/ltl2tgba.test,
src/tgbatest/ltlprod.test, src/tgbatest/mixprod.test,
src/tgbatest/readsave.test, src/tgbatest/reduccmp.test,
src/tgbatest/reductgba.test, src/tgbatest/scc.test,
src/tgbatest/spotlbtt.test, src/tgbatest/tgbaread.test,
src/tgbatest/tripprod.test: Adjust to run from a subdirectory.

configure.ac

@@ -23,7 +23,7 @@ AC_PREREQ([2.61])
 AC_INIT([spot], [0.4a])
 AC_CONFIG_AUX_DIR([tools])
 AC_CONFIG_MACRO_DIR([m4])
-AM_INIT_AUTOMAKE([1.11 gnits nostdinc tar-ustar color-tests])
+AM_INIT_AUTOMAKE([1.11 gnits nostdinc tar-ustar color-tests parallel-tests])
 
 # If the user didn't supplied a CFLAGS value,
 # set an empty one to prevent autoconf to stick -O2 -g here.