Created support for `MATCH` and `RETURN` queries using backslash command

[kenwoon]

Changes

MATCH, WHERE, WITH, and RETURN queries are made able to be parsed.

• Modified tokens in 'cypher.l'
• Modified grammars in 'cypher.y' grammars
• Created headers, objects, and executables by making Makefile

Instructions

1. Have Posgres 15 installed
2. Create a database and start the pgsql server
3. From the age repo directory, run the following lines of code

export PATH={location of pgsql-15}/bin:$PATH
export PGDATA={location of pgsql-15}/bin/data
export USE_PGXS=TRUE
flex -b -Cfe -p -p -o 'cypher.c' cypher.l
bison -d cypher.y
make

4. Run ./agesql
5. Enter a backslash \ followed by a newline to start typing in Cypher query
6. End each Cypher query with a semicolon ;

Example

MATCH (n:Person {age: 22}) RETURN n.name AS name; should return:

match = true
node {
	alias = n
	labels = Person
	property {
		identifier = age
		expression = 22
	}
}

return = true
item {
	expression = n.name
	alias = name
}

where = false

with = false