[indic] Flip default logic for double-halants in old-school

Oriya went down from 9 to 2.

BENGALI: 353725 out of 354188 tests passed. 463 failed (0.130722%)
DEVANAGARI: 707311 out of 707394 tests passed. 83 failed (0.0117332%)
GUJARATI: 366355 out of 366457 tests passed. 102 failed (0.0278341%)
GURMUKHI: 60729 out of 60747 tests passed. 18 failed (0.0296311%)
KANNADA: 951300 out of 951913 tests passed. 613 failed (0.0643966%)
MALAYALAM: 1048136 out of 1048334 tests passed. 198 failed (0.0188871%)
MYANMAR: 1115830 out of 1123883 tests passed. 8053 failed (0.716534%)
ORIYA: 42327 out of 42329 tests passed. 2 failed (0.00472489%)
SINHALA: 271596 out of 271847 tests passed. 251 failed (0.0923313%)
TAMIL: 1091754 out of 1091754 tests passed. 0 failed (0%)
TELUGU: 970555 out of 970573 tests passed. 18 failed (0.00185457%)

src/hb-ot-shape-complex-indic.cc

@@ -670,7 +670,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
    * is *not* a Halant after last consonant already.  We know that is the
    * case for Kannada, while it reorders unconditionally in other scripts,
    * eg. Malayalam, Bengali, and Devanagari.  We don't currently know about
-   * other scripts, so we whitelist Malayalam, Bengali, and Devanagari.
+   * other scripts, so we blacklist Kannada.
    *
    * Kannada test case:
    * U+0C9A,U+0CCD,U+0C9A,U+0CCD
@@ -693,9 +693,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
    */
   if (indic_plan->is_old_spec)
   {
-    bool disallow_double_halants = buffer->props.script != HB_SCRIPT_MALAYALAM &&
-				   buffer->props.script != HB_SCRIPT_BENGALI &&
-				   buffer->props.script != HB_SCRIPT_DEVANAGARI;
+    bool disallow_double_halants = buffer->props.script == HB_SCRIPT_KANNADA;
     for (unsigned int i = base + 1; i < end; i++)
       if (info[i].indic_category() == OT_H)
       {