[HarfBuzz] Contextual shaping of Malayalam post(pre)/below base forms

[Suresh P]

Hi,

In Malayalam some consonants like YA(യ), RA(ര) are quasi-vowels and they 
have post(pre)/below base forms. As per OT spec the pstf(pref) and blwf 
features are always applied and this leads to weird shaping when some 
consonants come as base. Eg. യ്ര, യ്ല, ര്ര, ല്ര. This is more prominent in 
reformed scripts because one can do away with these forms in traditional 
scripts. If these features can be applied as presentation forms, one can 
invoke contextual rules as and when required. But this will invariably 
break the current OT spec but then no spec is final.

So, to pun, this is feature request, too. :)

-suresh