[tests] Add test for fallback positioning with cluster_level > 0

For https://github.com/behdad/harfbuzz/pull/123
Currently fails.  Fix coming.

test/shaping/Makefile.am

@@ -38,6 +38,7 @@ CLEANFILES += \
 TESTS = \
 	tests/arabic-fallback-shaping.tests \
 	tests/arabic-feature-order.tests \
+	tests/cluster.tests \
 	tests/context-matching.tests \
 	tests/default-ignorables.tests \
 	tests/hangul-jamo.tests \

test/shaping/fonts/sha1sum/MANIFEST

@@ -6,6 +6,7 @@
 4cce528e99f600ed9c25a2b69e32eb94a03b4ae8.ttf
 5028afb650b1bb718ed2131e872fbcce57828fff.ttf
 57a9d9f83020155cbb1d2be1f43d82388cbecc88.ttf
+6466d38c62e73a39202435a4f73bf5d6acbb73c0.ttf
 757ebd573617a24aa9dfbf0b885c54875c6fe06b.ttf
 7e14e7883ed152baa158b80e207b66114c823a8b.ttf
 813c2f8e5512187fd982417a7fb4286728e6f4a8.ttf

test/shaping/tests/MANIFEST

@@ -1,5 +1,6 @@
 arabic-fallback-shaping.tests
 arabic-feature-order.tests
+cluster.tests
 context-matching.tests
 default-ignorables.tests
 hangul-jamo.tests

test/shaping/tests/cluster.tests

@@ -0,0 +1 @@
+fonts/sha1sum/6466d38c62e73a39202435a4f73bf5d6acbb73c0.ttf:--cluster-level=2:U+0078,U+030A,U+0058,U+030A:[gid2=0+1083|gid4=1@-555,-8+0|gid1=2+1200|gid4=3@-614,349+0]