Downcase SELQUANT_ALL string.
Use None, not 0, for no offset in ast.Lim.

This is an *expression*, not a literal integer.
Omit needless and unused SelCol AST node.
Beginnings of a BQL->SQL `compiler'.
Include the tables in compiled SELECTs.
Dot-qualify column names only when there is a specified table.
Add some more trivial bql2sql tests.
Fix typo: seltab, not seltabl.
More trivial bql2sql tests.
More trivial bql2sql tests.
Fix compiling ORDER BY and add trivial tests.
Add trivial LIMIT tests.