Replacing the antlr parsers solves multiple issues:
- Build warnings (issue #307)
- Build hacks: "-Xconversiontimeout 30000" and other Makefile magic
- Incorrect parsing of daap queries with sql wildcards (like 'tag:*tes%t_ng*')
- Infinite recursion/memory/CPU (issue #570 and #1248)
- systemd service file workarounds due to memory/CPU issue
- ANTLR3 being replaced with ANTLR4 (that doesn't support C file generation)
- Runtime dependency on antlr library
- Difficult installs of ANTLR3 on some systems (special install script)
songalbumid is used a lot in queries from Remote; computing the hash for
each row is a major waste of time on big libraries and slow machines, so
let's store the hash in the table.
This brings us to schema version 7.
