Add South-East Asian shaper

Handles Tai Tham, Cham, and New Tai Lue for now.

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

diff --git a/src/hb-ot-shape-complex-myanmar.cc b/src/hb-ot-shape-complex-myanmar.cc
index 5adcdfc..27a656d 100644
--- a/src/hb-ot-shape-complex-myanmar.cc
+++ b/src/hb-ot-shape-complex-myanmar.cc
@@ -28,7 +28,7 @@
 
 /* buffer var allocations */
 #define myanmar_category() complex_var_u8_0() /* myanmar_category_t */
-#define myanmar_position() complex_var_u8_1() /* myanmar_matra_category_t */
+#define myanmar_position() complex_var_u8_1() /* myanmar_position_t */
 
 
 /*