Add test for U+0A51

New Indic numbers are:

BENGALI: 353725 out of 354188 tests passed. 463 failed (0.130722%)
DEVANAGARI: 707307 out of 707394 tests passed. 87 failed (0.0122987%)
GUJARATI: 366355 out of 366457 tests passed. 102 failed (0.0278341%)
GURMUKHI: 60729 out of 60747 tests passed. 18 failed (0.0296311%)
KANNADA: 951201 out of 951913 tests passed. 712 failed (0.0747968%)
KHMER: 299071 out of 299124 tests passed. 53 failed (0.0177184%)
MALAYALAM: 1048136 out of 1048334 tests passed. 198 failed (0.0188871%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271662 out of 271847 tests passed. 185 failed (0.068053%)
TAMIL: 1091754 out of 1091754 tests passed. 0 failed (0%)
TELUGU: 970555 out of 970573 tests passed. 18 failed (0.00185457%)

Before 71c0a142 GURMUKHI used to be at 15,
because Uniscribe seems to allow this character standalone, but that looks
wrong.

test/shaping/tests/indic-syllable.tests

@@ -3,3 +3,5 @@ fonts/sha1sum/3d0b77a2360aa6faa1385aaa510509ab70dfbeff.ttf::U+0CF1:[gid1=0+1129]
 fonts/sha1sum/3d0b77a2360aa6faa1385aaa510509ab70dfbeff.ttf::U+0CF2:[gid2=0+1539]
 fonts/sha1sum/87f85d17d26f1fe9ad28d7365101958edaefb967.ttf::U+0980,U+0981:[anjibeng=0+520|candrabindubeng=0+0]
 fonts/sha1sum/85fe0be440c64ac77699e21c2f1bd933a919167e.ttf::U+0A15,U+0A51,U+0A47:[kaguru=0+1273|udaatguru=0@75,0+0|eematraguru=0@-40,0+0]
+fonts/sha1sum/1735326da89f0818cd8c51a0600e9789812c0f94.ttf::U+0A51:[uni25CC=0+1044|udaatguru=0+0]
+fonts/sha1sum/1735326da89f0818cd8c51a0600e9789812c0f94.ttf::U+25CC,U+0A51:[uni25CC=0+1044|udaatguru=0+0]