Implement lexer and parser for cypher commands with MATCH prototype. (#880)

This commit introduces the cypher .l and cypher.y file contains n a lexer
and grammar for handling cypher commands, respectively. The new files also
include a prototype function for the MATCH command, which will be further
developed in subsequent commits.

flex -b -Cfe -p -p -o ‘cypher.c’ cypher.l
bison -d cypher.y
6 files changed