Test cleanups and renaming.

Build tests in the tests/ directory instead of top, cleanup, rename,
and eliminate recursive make for the celt/ unit tests.
diff --git a/Makefile.am b/Makefile.am
index 056d447..6e9f3d5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2,7 +2,7 @@
 
 lib_LTLIBRARIES = libopus.la
 
-SUBDIRS = . celt/tests doc
+SUBDIRS = . doc
 
 INCLUDES = -I$(top_srcdir)/include -I$(top_srcdir)/celt -I$(top_srcdir)/silk -I$(top_srcdir)/silk/float -I$(top_srcdir)/silk/fixed
 
@@ -26,9 +26,9 @@
 
 noinst_HEADERS = $(OPUS_HEAD) $(SILK_HEAD) $(CELT_HEAD)
 
-noinst_PROGRAMS = opus_demo repacketizer_demo opus_compare test_opus_api test_opus_encode test_opus_decode
+noinst_PROGRAMS = opus_demo repacketizer_demo opus_compare tests/test_opus_api tests/test_opus_encode tests/test_opus_decode celt/tests/test_unit_cwrs32 celt/tests/test_unit_dft celt/tests/test_unit_entropy celt/tests/test_unit_laplace celt/tests/test_unit_mathops celt/tests/test_unit_mdct celt/tests/test_unit_rotation celt/tests/test_unit_types
 
-TESTS = test_opus_api test_opus_decode test_opus_encode
+TESTS = celt/tests/test_unit_types celt/tests/test_unit_mathops celt/tests/test_unit_entropy celt/tests/test_unit_laplace celt/tests/test_unit_dft celt/tests/test_unit_mdct celt/tests/test_unit_rotation celt/tests/test_unit_cwrs32 tests/test_opus_api tests/test_opus_decode tests/test_opus_encode
 
 opus_demo_SOURCES = src/opus_demo.c
 
@@ -41,14 +41,38 @@
 opus_compare_SOURCES = src/opus_compare.c
 opus_compare_LDADD = -lm
 
-test_opus_api_SOURCES = tests/test_opus_api.c tests/test_opus_common.h
-test_opus_api_LDADD = libopus.la -lm
+tests_test_opus_api_SOURCES = tests/test_opus_api.c tests/test_opus_common.h
+tests_test_opus_api_LDADD = libopus.la -lm
 
-test_opus_encode_SOURCES = tests/test_opus_encode.c tests/test_opus_common.h
-test_opus_encode_LDADD = libopus.la -lm
+tests_test_opus_encode_SOURCES = tests/test_opus_encode.c tests/test_opus_common.h
+tests_test_opus_encode_LDADD = libopus.la -lm
 
-test_opus_decode_SOURCES = tests/test_opus_decode.c tests/test_opus_common.h
-test_opus_decode_LDADD = libopus.la -lm
+tests_test_opus_decode_SOURCES = tests/test_opus_decode.c tests/test_opus_common.h
+tests_test_opus_decode_LDADD = libopus.la -lm
+
+celt_tests_test_unit_cwrs32_SOURCES = celt/tests/test_unit_cwrs32.c
+celt_tests_test_unit_cwrs32_LDADD = -lm
+
+celt_tests_test_unit_dft_SOURCES = celt/tests/test_unit_dft.c
+celt_tests_test_unit_dft_LDADD = -lm
+
+celt_tests_test_unit_entropy_SOURCES = celt/tests/test_unit_entropy.c
+celt_tests_test_unit_entropy_LDADD = -lm
+
+celt_tests_test_unit_laplace_SOURCES = celt/tests/test_unit_laplace.c
+celt_tests_test_unit_laplace_LDADD = -lm
+
+celt_tests_test_unit_mathops_SOURCES = celt/tests/test_unit_mathops.c
+celt_tests_test_unit_mathops_LDADD = -lm
+
+celt_tests_test_unit_mdct_SOURCES = celt/tests/test_unit_mdct.c
+celt_tests_test_unit_mdct_LDADD = -lm
+
+celt_tests_test_unit_rotation_SOURCES = celt/tests/test_unit_rotation.c
+celt_tests_test_unit_rotation_LDADD = -lm
+
+celt_tests_test_unit_types_SOURCES = celt/tests/test_unit_types.c
+celt_tests_test_unit_types_LDADD = -lm
 
 if CUSTOM_MODES
 pkginclude_HEADERS += include/opus_custom.h