Grammar revision for the big rename / PSYC 1.0 revision.

(pair) ::= (key) "\t" [ (length) ] "\t" (value) 
(header) ::= (modifier) (pair) "\n"
(message) ::= { (header) } (method) "\n" (body)
(routes) ::= { (header) }
(packet) ::= (routes) "\n" (message) "\n.\n"

Lexer info: (value) may no longer contain "\n" unless made transparent by presence of (length). Thus non-length capable implementations will no longer be able to handle multi-line variables. This is a simplification: No more escaping at all.