Third-level la needs drawing

[simoncozens]

We have a subjoined form of LA: (uni1B2E.sub, formed with e.g. ᬦ᭄ᬮ)

However (per #3), when la is used as the third level in a stack (e.g. ᬦ᭄ᬤ᭄ᬮ) it takes a different form, with a little fish-hook at the end (shown here in Vimala):

We need this form drawing before we can correct support third-level la.