Switch to the preferred parallel automake test harness

Automake "strongly discourages" use of the serial driver, and switching
to the preferred parallel driver allows make -j4 check to run in about
half the time on a four core (not thread) host.

* Makefile.am (TESTS, TESTS_ENVIRONMENT): run ./check-guile from
test-suite/, not here.
* check-guile.in: let test harness handle progress output.
* configure.ac (AM_INIT_AUTOMAKE): allow parallel testing.
* test-suite/Makefile.am (SCM_TESTS): remove non-tests.
(EXTRA_DIST): move non-tests here.
(TESTS): include SCM_TESTS (now driven from here).
(TEST_EXTENSIONS): allow customization for .scm and .test.
(TESTS_ENVIRONMENT): stop defining (user only).
(AM_TESTS_ENVIRONMENT): replaces TESTS_ENVIRONMENT; drop guile.
(SCM_LOG_COMPILER): run .scm tests via meta/guile.
(AM_SCM_LOG_FLAGS): keep --no-auto-compile for .scm tests.
(TEST_LOG_DRIVER): run .test tests via custom automake ./driver.
* test-suite/driver: add automake test driver.

Makefile.am

@@ -85,9 +85,6 @@ EXTRA_DIST = LICENSE HACKING GUILE-VERSION			\
 	     .guix/modules/guile-package.scm			\
 	     .guix/manifest.scm
 
-TESTS = check-guile
-TESTS_ENVIRONMENT = @LOCALCHARSET_TESTS_ENVIRONMENT@
-
 ACLOCAL_AMFLAGS = -I m4
 
 CLEANFILES = libguile/guile-procedures.txt