Add libgit2-pgsql stub.
Implement connect/free, create table and indexes, prepare read statement.
Correctly avoid creating existing indexes. Set giterr on error.
Switch to 4-space indentation.
Implement read.
Refactor duplicate code to complete_pq_exec function.
Prepare read_header statement.
Implement read_header.
Implement exists.
Prepare write statement.
Implement write.
Rename pgsql_backend to pgsql_odb_backend.