Revert "Allow clusters to start with zero-width characters"

This reverts commit 3e0fc64da064b8c4156daf53242b8eeb47830f64.

Bug: 22589743
Bug: 22121742
Change-Id: I7b482ffb8a0ee174ddc804aa890de45bdbd758e3
1 file changed
tree: 78fc43e7c9c04932a0996490a8e6d2ddb0ab40f2
  1. include/
  2. libs/
  3. sample/