[Indic] Adjust position for split matras

We are going to split matras without a Unicode decompositions in a way
that the second half takes the codepoint of the whole matra.  So,
position them where the second half is supposed to end up.

src/hb-ot-shape-complex-indic-private.hh

@@ -121,11 +121,11 @@ enum indic_matra_category_t {
    * We have to figure out what to do with them.
    */
   INDIC_MATRA_CATEGORY_BOTTOM_AND_RIGHT		= POS_POST_M,
-  INDIC_MATRA_CATEGORY_LEFT_AND_RIGHT		= POS_PRE_M,
+  INDIC_MATRA_CATEGORY_LEFT_AND_RIGHT		= POS_POST_M,
   INDIC_MATRA_CATEGORY_TOP_AND_BOTTOM		= POS_BELOW_M,
   INDIC_MATRA_CATEGORY_TOP_AND_BOTTOM_AND_RIGHT	= POS_POST_M,
-  INDIC_MATRA_CATEGORY_TOP_AND_LEFT		= POS_PRE_M,
-  INDIC_MATRA_CATEGORY_TOP_AND_LEFT_AND_RIGHT	= POS_PRE_M,
+  INDIC_MATRA_CATEGORY_TOP_AND_LEFT		= POS_ABOVE_M,
+  INDIC_MATRA_CATEGORY_TOP_AND_LEFT_AND_RIGHT	= POS_POST_M,
   INDIC_MATRA_CATEGORY_TOP_AND_RIGHT		= POS_POST_M,
 
   INDIC_MATRA_CATEGORY_INVISIBLE		= INDIC_MATRA_CATEGORY_NOT_APPLICABLE,