Format for Lojban definitions of Lojban brivla

[Pierre Abbat <phma@oltronics.net>]

I propose that when defining a brivla in Lojban, ko'a, ko'e, ... be used for
the terbri, and da, de, di be used for variables internal to the definition.
If the first pro-sumti is omitted, it is assumed to be ko'a. For example:

mudri: marji lo stani be lo tricu be ko'e
panzi: da tsiju ko'e ko'a

phma