[feature] Mail: added address conversion functions
[fix] Mail: to_name shouldn't be tagged with @stringifier
[feature] compiler, database, sql: Added a sql query node
[feature] compiler, database, sql: First draft of typing of sql query
squash [feature] compiler, database, sql: Added a sql query node
[feature] compiler, database, sql: First draft of syntax of sql query
[feature] compiler, database, sql: Added `bind expression to sql queries
[fix] apigenlib:  Arrange to retain socket between calls.
[fix] apigenlib:  Tidy up.
[feature] runtime, database, postgres: Simplify Postgres runtime
[feature] database, postgres: Added skeleton for postgres backend
[enhance] commpiler: Remove @spawn restriction (@spawn directive could only works with syntactic record)
[enhance] compiler, database, postgres: Generate databases objects
[feature] stdlib, postgres: Added Postgres.get_name
[feature] stdlib, database, postgres: Added prepared statement to DbPostgres.open (compiler api)
[feature] compiler, database: Added SqlAccess node
[feature] compiler, database, postgres: Generates prepared statement
[enhance] compiler, utils: Added QmlAstWalk.DbWalk.Query
[feature] stdlib, postgres: Added Postgres.serialize
[cleanup] stdlib, postgres: Remove Postgres.create_enum